Vacuum applied to EGR at idle
02-10-2002, 07:05 PM
#1
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Vacuum applied to EGR at idle
My scantool tells me that the ECM is giving the EGR valve vacuum at idle. From my understanding the EGR shouldn't be used at idle, so what would cause this? I was thinking my EGR vacuum solenoid but I would like a second opinion. Thanks
02-10-2002, 07:23 PM
#2
PP,
I asked my dog, and he said "That ain't right." (He frequently uses "ain't", but he's just a dog.)
He also asked what kind of scanner you were using, since he specifically remembers that some of the earlier software scanners for laptops would provide erroneous readings of some engine parameters, and these were attributed to software glitches. According to him "That ain't right", either.
He says there should be no EGR vacuum at idle, and if you really do have vacuum there the solenoid, ECM output, or solenoid wiring "ain't right" as well. You should check with a vacuum gauge if you have one. (I added that part.)
I'd have him type this himself since he's much faster at it than I am. But the last time I allowed him to surf the web his toenails really screwed my keyboard, and I caught him checking out poodles on one of "those" sites...
Oh, now he's annoyed since I'm telling stories about him - he's so freakin' sensitive.
I asked my dog, and he said "That ain't right." (He frequently uses "ain't", but he's just a dog.)
He also asked what kind of scanner you were using, since he specifically remembers that some of the earlier software scanners for laptops would provide erroneous readings of some engine parameters, and these were attributed to software glitches. According to him "That ain't right", either.
He says there should be no EGR vacuum at idle, and if you really do have vacuum there the solenoid, ECM output, or solenoid wiring "ain't right" as well. You should check with a vacuum gauge if you have one. (I added that part.)
I'd have him type this himself since he's much faster at it than I am. But the last time I allowed him to surf the web his toenails really screwed my keyboard, and I caught him checking out poodles on one of "those" sites...
Oh, now he's annoyed since I'm telling stories about him - he's so freakin' sensitive.
02-10-2002, 08:06 PM
#3
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
I use an OTC scanner and at idle the EGR position reads 'ON' which the manual says vacuum is being applied to the EGR valve. I have not checked with a vacuum gage myself.
02-10-2002, 08:39 PM
#4
PP,
My little buddy says the OTC scanners are pretty reliable, and there may be a problem with the EGR solenoid. The ECM will look for a resistance load from the EGR solenoid, and will set a DTC is there is a resistance out of an allowable range. If you have no error codes, that isn't likely an issue.
The scanner may be presuming that there is an EGR problem based on the ECM parameters and the MAP sensor readings. A higher than expected MAP signal (inadequate vacuum) may be interpreted as an intake leak or EGR that is partially open. There are many other possible reasons for a high MAP signal, and I'm not sure how the scanner could presume an EGR problem unless there was an ECM command to open it. This shouldn't occur unless the TPS is relatively low and the engine RPMs are above 1,500 or so (highway cruise mode). On S-D and TBI cars, the MAP has to be fairly low as well to indicate part-throttle cruise operation before the EGR will enable.
What year/model/fuel system are you working with? If it's a TPI, there is a diagnostic temperature sensor on the EGR valve which is used to indicate EGR function. I suppose the scanner could be reacting to that data and presuming some EGR opening, but that would be pretty speculative.
You've got the little guy guessing now. And he's just a dog after all...
My little buddy says the OTC scanners are pretty reliable, and there may be a problem with the EGR solenoid. The ECM will look for a resistance load from the EGR solenoid, and will set a DTC is there is a resistance out of an allowable range. If you have no error codes, that isn't likely an issue.
The scanner may be presuming that there is an EGR problem based on the ECM parameters and the MAP sensor readings. A higher than expected MAP signal (inadequate vacuum) may be interpreted as an intake leak or EGR that is partially open. There are many other possible reasons for a high MAP signal, and I'm not sure how the scanner could presume an EGR problem unless there was an ECM command to open it. This shouldn't occur unless the TPS is relatively low and the engine RPMs are above 1,500 or so (highway cruise mode). On S-D and TBI cars, the MAP has to be fairly low as well to indicate part-throttle cruise operation before the EGR will enable.
What year/model/fuel system are you working with? If it's a TPI, there is a diagnostic temperature sensor on the EGR valve which is used to indicate EGR function. I suppose the scanner could be reacting to that data and presuming some EGR opening, but that would be pretty speculative.
You've got the little guy guessing now. And he's just a dog after all...
02-10-2002, 09:02 PM
#5
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
It's a 1989 Formula 350 with MAF TPI. Is there a way to test the egr solenoid?
02-11-2002, 08:40 PM
#7
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Car: 1984 Z28
Engine: 454
Transmission: Th400
Axle/Gears: 3.73
One way to test it is to replace it. It only takes 10 minutes to change and if doesn't fix it take it back. It is the most common part to fail so chances are it will fix the problem.
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02-11-2002, 09:36 PM
#8
PP,
Hold on a minute - let me get my dog inside...
:lala:
O.K. We're set.
If you have a vacuum gauge, you can check the mechanical function of the EGR solenoid pretty easily. A DMM or plain old analog ohmmeter will do the rest.
Disconnect the electrical connector from the EGR solenoid. Start the engine and test the vacuum on the line that is attached to the 'A' port on the solenoid. There should be no vacuum in the idle position, and vacuum should be present when the throttle is at the 10-15% open range. The source for this vacuum line is a port in the throttle body that is just in front of the lower edge of the throttle plates.
Reattach the vaccum line to the 'A' port if that checks out O.K. Keep the electrical connector off for now. Attach the gauge to the 'B' port on the solenoid. With the engine running and the throttle at about 10-15% (so there should be vacuum on the 'A' port), there should be no vacuum on the 'B' port. This would indicate that the solenoid is closed properly. If you can read vacuum, the solenoid is mechanically sticking or leaking internally, and should be replaced.
If everything is correct to this point, reconnect the line and test the resistance of the solenoid coil with an ohmmeter. The coil should be in the 35-50 ohm range at a minimum, but not over 100 ohms.
Since you have a MAF TPI, there should be a diagnostic temperature sensor on the base of the EGR valve. This sensor may be reading excessive temperature and causing the DTC. The excessive reading could be from a failing sensor, shorted sensor wiring harness, or an EGR valve that is leaking or sticking open partially.
You can test the resistance of the sensor to ground, but the connector is difficult to get at back near the distributor. If you do manage to get the connector open, the resistance at a given temperatue should match the table:
If the sensor resistance appeares to be correct at a known intake temperature (on a cold engine) then consider the possibility of a sticky, carboned, or leaking EGR valve. If the sensor is reading incorrectly, the result is still the same - you'll be pulling the plenum to replace the valve. If you do have to remove it, remember a few things:
1. Use anti-sieze when reassembling any bolts in to aluminum;
2. Don't risk using a cheaper aftermarket EGR valve on these engines;
3. It's an excellent excuse to port the plenum, since you're already buying gaskets anyway.
See, my dog says there's always a bright side.
Hold on a minute - let me get my dog inside...
:lala:
O.K. We're set.
If you have a vacuum gauge, you can check the mechanical function of the EGR solenoid pretty easily. A DMM or plain old analog ohmmeter will do the rest.
Disconnect the electrical connector from the EGR solenoid. Start the engine and test the vacuum on the line that is attached to the 'A' port on the solenoid. There should be no vacuum in the idle position, and vacuum should be present when the throttle is at the 10-15% open range. The source for this vacuum line is a port in the throttle body that is just in front of the lower edge of the throttle plates.
Reattach the vaccum line to the 'A' port if that checks out O.K. Keep the electrical connector off for now. Attach the gauge to the 'B' port on the solenoid. With the engine running and the throttle at about 10-15% (so there should be vacuum on the 'A' port), there should be no vacuum on the 'B' port. This would indicate that the solenoid is closed properly. If you can read vacuum, the solenoid is mechanically sticking or leaking internally, and should be replaced.
If everything is correct to this point, reconnect the line and test the resistance of the solenoid coil with an ohmmeter. The coil should be in the 35-50 ohm range at a minimum, but not over 100 ohms.
Since you have a MAF TPI, there should be a diagnostic temperature sensor on the base of the EGR valve. This sensor may be reading excessive temperature and causing the DTC. The excessive reading could be from a failing sensor, shorted sensor wiring harness, or an EGR valve that is leaking or sticking open partially.
You can test the resistance of the sensor to ground, but the connector is difficult to get at back near the distributor. If you do manage to get the connector open, the resistance at a given temperatue should match the table:
If the sensor resistance appeares to be correct at a known intake temperature (on a cold engine) then consider the possibility of a sticky, carboned, or leaking EGR valve. If the sensor is reading incorrectly, the result is still the same - you'll be pulling the plenum to replace the valve. If you do have to remove it, remember a few things:
1. Use anti-sieze when reassembling any bolts in to aluminum;
2. Don't risk using a cheaper aftermarket EGR valve on these engines;
3. It's an excellent excuse to port the plenum, since you're already buying gaskets anyway.
See, my dog says there's always a bright side.
Last edited by Vader; 03-04-2002 at 09:00 AM.
02-11-2002, 10:04 PM
#9
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no scantool will actually say "vacuum applied to egr" not on our camaros-its a pulse width modulated solenoid that has control on the valve which is also dependent on a certain backpressure to allow internal passages to close and let vacuum lift the pintle-what is the symptom were chasing here? or code? or did you see egr duty % or a parameter close to that?
02-11-2002, 10:52 PM
#10
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Im trying to fix my rough idle. My car wouldn't pass emissions either and I have read EGR at idle causes weak combustion which could have shot my HC output up. I also get 11mpg. I will be testing all aspects of the EGR system tomorrow as described by Vader and I should have some feedback tomorrow night. Yes there is a EGR duty cycle, what should I look for data wise from that?
Last edited by PLANT PROTECTION; 02-12-2002 at 12:47 AM.
02-12-2002, 01:43 AM
#11
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ok- what are your hc #'s at idle? i think that the egr valve is close to last to suspect as a problem, but it may be. how much o2 is left over when the hc numbers are too high? how much is too high? have you carb sprayed ALL the multiple joints in that tpi intake setup? if you did you have no vacuum leaks? i cant believe that there are none anywhere. the diag. temp sensor is there on the valve to prove out egr flow to the ecm if the sensor was not working or the egr passages were plugged then you would be getting a code 32 (pretty sure its 32,off the top of my cranium) which indicates egr system problems. do you have the code? give me the co numbers too just chasing hc in this situation can be counterproductive to solving the big picture. from what i gather the smog check numbers you are seeing are leading you towards a lean misfire? all the other gasses are ok, except oxygen which should be as skewed as the hc's are. is that the situation here? if you give me some exhaust gas readings i will be able to tell what is going into the combustion chambers and whats happening as the fuel burns or not burns or any other myriad malfunctions that take you further from the magic 14.7 to 1 we all be looking for. go for it and check the egr-but i think the answer is elsewhere. seeya frank to recap need HC, CO, O2, CO2,NOX-nox is cal. only if it dosent apply here skip it. at all (both) test rpms too.
02-12-2002, 02:55 PM
#12
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Car: 1984 Z28
Engine: 454
Transmission: Th400
Axle/Gears: 3.73
If you are having rough idle problems try cleaning out the idle air passage of the throttle body by shooting gumout through it. It worked for me.
02-13-2002, 09:49 PM
#13
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
I tested all the aspects of the EGR system yesterday. The valve itself can be pushed up easily and will hold vacuum. The temp sensor matches impedence values and the solenoid is new. I also cleaned out the IAC passages. My idle is still rough and performs poorly form idle-3000RPM. I friend of mine that rode in the car said it felt like a missfire but all of my ignition components have 2k miles on them. I was leaning toward the EGR problem because I read too much EGR when not needed causes weak ignition dispite new parts. Here are my emission numbers:
HC-2.79 _ 1.40 is the limit
CO-0.10 _ 20.00 is the limit
NO-0.80 _ 3.00 is the limit
Oxygen isn't tested for in my area. I was thinking I was running lean because my CO reading is so low. These numbers are with 2 brand new cats also. What should I do now?
HC-2.79 _ 1.40 is the limit
CO-0.10 _ 20.00 is the limit
NO-0.80 _ 3.00 is the limit
Oxygen isn't tested for in my area. I was thinking I was running lean because my CO reading is so low. These numbers are with 2 brand new cats also. What should I do now?
02-14-2002, 01:24 AM
#14
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hey pp-please check the format of the gasses-should be more layed out like: HC 279 ppm 140 ppm is max limit
CO 0.10% 2.0% is max limit
NO 0.80% 3.00% is max limit
where ppm=parts per million and percent is self explanatory just check the paperwork again and see because the numbers are screwy specially the CO, which, btw, if it is really .1% shows air fuel is perfect at 14.7 to 1 so what you have here is a misfire in a cylinder or 2. hc=unburnt fuel at what rpm are these #'s sampled at? does the readings clean up at a higher rpm-is the car completely hot hot more than you would like to see but a hot engine will get you thru a smog check easier check cap rotor plugs plug wires at both connection ends is timing set? the hc numbers are close that even retarding timing to say about 2 btdc could induce excess hc to burn in ex.manifold-will timing be checked again at the re-test? lemme know-any CO2 or O2 #'s to supply? can you ask when the test is performed to have those gasses included in the printout?
CO 0.10% 2.0% is max limit
NO 0.80% 3.00% is max limit
where ppm=parts per million and percent is self explanatory just check the paperwork again and see because the numbers are screwy specially the CO, which, btw, if it is really .1% shows air fuel is perfect at 14.7 to 1 so what you have here is a misfire in a cylinder or 2. hc=unburnt fuel at what rpm are these #'s sampled at? does the readings clean up at a higher rpm-is the car completely hot hot more than you would like to see but a hot engine will get you thru a smog check easier check cap rotor plugs plug wires at both connection ends is timing set? the hc numbers are close that even retarding timing to say about 2 btdc could induce excess hc to burn in ex.manifold-will timing be checked again at the re-test? lemme know-any CO2 or O2 #'s to supply? can you ask when the test is performed to have those gasses included in the printout?
02-14-2002, 03:06 AM
#15
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Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
a compression test and or a power balance test would be advisable as well... check the ignition components over and also check for vacuum leaks on indvidual cyl intake runners one anything that is close to just one cylinder...
having new cats can mask a problem making it hard to diagnose a problem just looking at the gasses... the two gasses that GGA is asking about are very important in using gasses to diag...
I hate throwing out SWAG's (stupid wild a$$ guesses) but...... from the readings on the scan tool on the egr percent, the rough idle and the excessive HC readings I might suspect the pintle on the EGR valve might not be seating all the way... this would allow exhuast gasses back into the combustion chamber diluting the air fuel mixture giving you poor or incomplete combustion...
check all previously recommended things first I don't want to be responsible for unneeded repairs...
I also would like to see those additional gasses as well as the format for them...
zroc
having new cats can mask a problem making it hard to diagnose a problem just looking at the gasses... the two gasses that GGA is asking about are very important in using gasses to diag...
I hate throwing out SWAG's (stupid wild a$$ guesses) but...... from the readings on the scan tool on the egr percent, the rough idle and the excessive HC readings I might suspect the pintle on the EGR valve might not be seating all the way... this would allow exhuast gasses back into the combustion chamber diluting the air fuel mixture giving you poor or incomplete combustion...
check all previously recommended things first I don't want to be responsible for unneeded repairs...
I also would like to see those additional gasses as well as the format for them...
zroc
02-14-2002, 10:50 AM
#16
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Here is a visual to help you help me. I hope its not too big.
02-14-2002, 12:08 PM
#17
PP,
Let's pull together all the data to this point. Feel free to correct or edit any of these statements that are incorrect or incomplete:
1. Your HC emissions are high;
2. The idle quality is poor;
3. Power is not good up to 3,000 RPM;
4. The OTC scanner is indicating that there are EGR solenoid pulses at idle;
5. You are averaging 11MPG;
6. You have an '89 TPI 350 with a MAF;
7. The EGR valve is free to move and the diaphragm will hold vacuum;
8. You have a new EGR solenoid and are getting the same symptoms as with the old one;
9. The EGR diagnostic temperature sensor has reasonable resistances at a given temperature;
10. You have twin cat converters that are relatively new;
11. The ignition components are recently replaced;
12. You have cleaned the throttle body and idle air control passages;
13. The data from the emissions test is from August of last year.
Now to fill in the gaps:
A. Are there any modifications to the engine, and what are they?
B. What is the operating coolant temperature of the engine, fully warmed?
C. What is the intake vacuum at idle?
D. What is the idle RPM?
E. Are there any DTCs in the ECM memory?
Provide that data and we can get a little closer to the problem. My dog is getting anxious...
Let's pull together all the data to this point. Feel free to correct or edit any of these statements that are incorrect or incomplete:
1. Your HC emissions are high;
2. The idle quality is poor;
3. Power is not good up to 3,000 RPM;
4. The OTC scanner is indicating that there are EGR solenoid pulses at idle;
5. You are averaging 11MPG;
6. You have an '89 TPI 350 with a MAF;
7. The EGR valve is free to move and the diaphragm will hold vacuum;
8. You have a new EGR solenoid and are getting the same symptoms as with the old one;
9. The EGR diagnostic temperature sensor has reasonable resistances at a given temperature;
10. You have twin cat converters that are relatively new;
11. The ignition components are recently replaced;
12. You have cleaned the throttle body and idle air control passages;
13. The data from the emissions test is from August of last year.
Now to fill in the gaps:
A. Are there any modifications to the engine, and what are they?
B. What is the operating coolant temperature of the engine, fully warmed?
C. What is the intake vacuum at idle?
D. What is the idle RPM?
E. Are there any DTCs in the ECM memory?
Provide that data and we can get a little closer to the problem. My dog is getting anxious...
02-14-2002, 03:41 PM
#18
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Here is the info to fill in the gaps:
A. I have Accel 21# injectors with a AFPR set at 44PSI
B. While driving 195deg and after sitting idle 210deg
C. 15-16.5 cmHG at idle, number varies with roughness
D. Idle RPM in Park 700-800RPM
E. No codes are pulled
A. I have Accel 21# injectors with a AFPR set at 44PSI
B. While driving 195deg and after sitting idle 210deg
C. 15-16.5 cmHG at idle, number varies with roughness
D. Idle RPM in Park 700-800RPM
E. No codes are pulled
02-14-2002, 10:34 PM
#19
PP,
I hope you meant to say "15-16½ INCHES mercury, not cm. There's a huge difference there. Even at that, 15" Hg on a stock engine is a bit low, so the sticky/leaking EGR theory may be valid.
Have you tried running with the vacuum line to the EGR unplugged? Have you tried capping the power brake booster vacuum line? How about plugging the PCV system, too? That vacuum seems too low for some reason, and if the intake and injectors are sealed, you're leaking somewhere (my guess).
The temperature should be adequate for good combustion, and the free idle speed seems about right (maybe a bit low).
I am a little unclear on the fuel pressure, though. Is it at 44PSI while running with the vacuum line attached, or is that the standing pressure with the engine off?
I hope you meant to say "15-16½ INCHES mercury, not cm. There's a huge difference there. Even at that, 15" Hg on a stock engine is a bit low, so the sticky/leaking EGR theory may be valid.
Have you tried running with the vacuum line to the EGR unplugged? Have you tried capping the power brake booster vacuum line? How about plugging the PCV system, too? That vacuum seems too low for some reason, and if the intake and injectors are sealed, you're leaking somewhere (my guess).
The temperature should be adequate for good combustion, and the free idle speed seems about right (maybe a bit low).
I am a little unclear on the fuel pressure, though. Is it at 44PSI while running with the vacuum line attached, or is that the standing pressure with the engine off?
02-14-2002, 10:53 PM
#20
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Car: 1987 Monte Carlo SS
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Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
The fuel pressure is tested at idle with the AFPR vacuum line off. Ill try capping some of the vacuum stuff like brake booster and PCV. What is a good number for idle vacuum?
02-15-2002, 01:21 AM
#21
Senior Member
here is another quick thought -has anyone checked the charcoal cannister for a faulty purge valve (solenoid) pull the vent line and give er a whiff-bigtime fuel? wet w/gas? hows the air management valve? pull the outlet hoses and make sure the air is going downstream and upstream as required-cold engine is air to exhaust manifolds and some out the discharge tube. warm engine is air to cat, none to ex. manifolds. mileage will plummet also if the air switch valve isnt diverting al air down to cat. during normal engine operation when warmed up. pull valve off air pump supply tube and shake it -do it be rattling? first sign of something awry within it.if you are getting air injected into the ex.manifolds during warm engine normal driving the o2 sensor will pick up on the extra o2 in the exhaust stream (which shouldnt be there) and interpret it as lean(extra o2= lean)and the ecm will start happily adding fuel till 128 comes round again but guess what? the fuel wasnt required to start with and hc is one byproduct-out here in ca all emission readings are either parts per million or percentages checked the net for conversion help and it seems to be not such an easy task requires more data on the gasses i requested earlier-ck this for more info on that
http://www.servicemycar.com/gpm.htm if anyone has a quick n dirty yet reasonabl accurate conversion method-speak up tasks: verify c.cannister isnt allowing gas (raw or vapors) incorrectly. verify proper function of a.i.r. switch valve (pedes) in gm speak seeeeeeeya
http://www.servicemycar.com/gpm.htm if anyone has a quick n dirty yet reasonabl accurate conversion method-speak up tasks: verify c.cannister isnt allowing gas (raw or vapors) incorrectly. verify proper function of a.i.r. switch valve (pedes) in gm speak seeeeeeeya
02-15-2002, 08:31 AM
#23
Ward,
You could probably borrow my dog, but it looks like you could do a bit better if you borrowed an "ape". This one has his head on straight.
- - - - - - - - - - - - - - - - - - - - - - - - -
PP,
The fuel pressure is perfect, so that isn't likely an issue.
- - - - - - - - - - - - - - - - - - - - - - - - -
GGA,
Good call on the A.I.R. valve. I would suspect that a leaking/stuck valve in the port position would cause those symptoms, but would also cause a huge offset in the BLM numbers - then again, we didn't see the complete results of the scan, did we?
You could probably borrow my dog, but it looks like you could do a bit better if you borrowed an "ape". This one has his head on straight.
- - - - - - - - - - - - - - - - - - - - - - - - -
PP,
The fuel pressure is perfect, so that isn't likely an issue.
- - - - - - - - - - - - - - - - - - - - - - - - -
GGA,
Good call on the A.I.R. valve. I would suspect that a leaking/stuck valve in the port position would cause those symptoms, but would also cause a huge offset in the BLM numbers - then again, we didn't see the complete results of the scan, did we?
02-18-2002, 02:47 AM
#24
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Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
Just another I have been following... so TTT
if you still have that scan tool, I would appreciate it if you could tell us the O2 voltage at cold start idle, warm idle, steady cruise, and the cross counts on the last two modes...
thanks
zroc
if you still have that scan tool, I would appreciate it if you could tell us the O2 voltage at cold start idle, warm idle, steady cruise, and the cross counts on the last two modes...
thanks
zroc
02-19-2002, 08:08 PM
#25
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Car: 1987 Monte Carlo SS
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I get you that o2 info as soon as I can get the scanner on there again. Another thing I noticed is after it has been sitting and I start it up and get ready to go, it hesitates and nearly stalls but it will only do it once when cold and that is it. More things wrong or going wrong.
02-20-2002, 03:10 AM
#26
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Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
at your earliest conveniece...
man if you can post all the sensor data or readings from the ecm at different throttle inout or situations that would be great... but if you can only give the idle and possibly the steady cruise readings I will live...
I lke to find (or help find) solutions to prolems like this... but most of all I want to find it in the most efficient manner... having a scan tool is a great advantage... it may not be the solution but it can help to narrow down the problem area a lot easier...
zroc
am I going to get in trouble for giving this another bump???
man if you can post all the sensor data or readings from the ecm at different throttle inout or situations that would be great... but if you can only give the idle and possibly the steady cruise readings I will live...
I lke to find (or help find) solutions to prolems like this... but most of all I want to find it in the most efficient manner... having a scan tool is a great advantage... it may not be the solution but it can help to narrow down the problem area a lot easier...
zroc
am I going to get in trouble for giving this another bump???
02-20-2002, 08:15 AM
#27
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Originally posted by Vader
PP,
I asked my dog, and he said "That ain't right." (He frequently uses "ain't", but he's just a dog.)
He also asked what kind of scanner you were using, since he specifically remembers that some of the earlier software scanners for laptops would provide erroneous readings of some engine parameters, and these were attributed to software glitches. According to him "That ain't right", either.
He says there should be no EGR vacuum at idle, and if you really do have vacuum there the solenoid, ECM output, or solenoid wiring "ain't right" as well. You should check with a vacuum gauge if you have one. (I added that part.)
I'd have him type this himself since he's much faster at it than I am. But the last time I allowed him to surf the web his toenails really screwed my keyboard, and I caught him checking out poodles on one of "those" sites... Oh, now he's annoyed since I'm telling stories about him - he's so freakin' sensitive.
PP,
I asked my dog, and he said "That ain't right." (He frequently uses "ain't", but he's just a dog.)
He also asked what kind of scanner you were using, since he specifically remembers that some of the earlier software scanners for laptops would provide erroneous readings of some engine parameters, and these were attributed to software glitches. According to him "That ain't right", either.
He says there should be no EGR vacuum at idle, and if you really do have vacuum there the solenoid, ECM output, or solenoid wiring "ain't right" as well. You should check with a vacuum gauge if you have one. (I added that part.)
I'd have him type this himself since he's much faster at it than I am. But the last time I allowed him to surf the web his toenails really screwed my keyboard, and I caught him checking out poodles on one of "those" sites...
Oh, now he's annoyed since I'm telling stories about him - he's so freakin' sensitive. 
02-23-2002, 05:49 AM
#28
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Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
GGA...
correct me if I'm wrong here but if we had too much fuel (raw fuel or vapors from canister purge) the CO levels would be out of spec before hc... not seeing that here (only referenece being HC and CO readings)...
also... we should not have EVAP purge at idle... (I may have just answered my own question here)...
still wondering about the egr %...
man... O2 and CO2 readings would help alot...
PP, do you know some one that might have a 4 gas (CO, HC, O2, CO2) analyzer???
also... when taking the idle vacuum reading how does the needle behave???
zroc
correct me if I'm wrong here but if we had too much fuel (raw fuel or vapors from canister purge) the CO levels would be out of spec before hc... not seeing that here (only referenece being HC and CO readings)...
also... we should not have EVAP purge at idle... (I may have just answered my own question here)...
still wondering about the egr %...
man... O2 and CO2 readings would help alot...
PP, do you know some one that might have a 4 gas (CO, HC, O2, CO2) analyzer???
also... when taking the idle vacuum reading how does the needle behave???
zroc
Last edited by zroc; 02-23-2002 at 05:55 AM.
02-23-2002, 07:07 AM
#29
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Car: 89RSconvtZZ4TPI
Engine: ZZ4TPI
Transmission: 700R4 TRIPP TRANNY
Just to back up the A.I.R. theory, my ZZ4TPI MAP system was running pig rich, O2 sensor not reporting ready. not going into closed loop, O2 cross counts not moving. I replaced my leaking header gaskets but still a problem. When we chopped the AIR lines off the SLP headers, we taped the holes and ran bolts down them. Apparently air was leaking by the fine threads and giving the O2 sensor fits. I had the holes welded closed yesterday and all seems to be normal now.
Not fun when the injectors go from a normal 1.8pw to 4.5pw at idle! Cause for lots of black smoke and rough running!
Not fun when the injectors go from a normal 1.8pw to 4.5pw at idle! Cause for lots of black smoke and rough running!
02-23-2002, 07:53 PM
#30
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
I did check the egr duty cycle % and it was 0% at idle and 100% whenever I gave it any gas, seemed odd to me. The needle of the vacuum reading does up when idle rpm decreases and down when idle rpm increases. As for a sniffer, I don't know anyone with one. I should get my on the scanner Sunday or Monday for an update.
02-24-2002, 12:01 AM
#31
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the solenoid is functioning perfectly if you see vacuum when revving. pulse width modulation. proper egr operation(in a system utilizing a positive b.p, egr valve) requires a certain amount of backpressure in order to have the valve lift the pintle from the seat and allow flow.the solenoid will almost always allow a vacuum leak like that to happen-out the other port on the solenoid also-thats why the solenoids start life with a foamie filter on them. keen and neato baby air filter. stuff a rag in the tailpipe-someone holds it in place and then rev the motor and see the valve do its valve thing. haha-remember the movie with eddie murphy and he says to that other cop "i aint fallin for no banana in my tailpipe" cuz bro had no rythym-hilarious-back on topic now-ok im done seeya later :rockon: :lala: :hail:
02-24-2002, 03:11 PM
#32
PP,
So you still have 15-16½" Hg vacuum at idle. Have you capped all the vacuum lines to test their integrity? Don't forget the brake booster, PCV, and EVAP/EGR lines.
In a holding pattern...
So you still have 15-16½" Hg vacuum at idle. Have you capped all the vacuum lines to test their integrity? Don't forget the brake booster, PCV, and EVAP/EGR lines.
In a holding pattern...
02-24-2002, 03:23 PM
#33
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
I got my car on the scanner today. Off idle, it wouldn't peg to 4.4v and while crusing it varied from .7 to 3v. I replaced it and steadily pulls throughout the RPM range, but the power is still lacking. My o2 voltage was damn near .000154 at all times, not good. When I tried changing it a week or so ago I (seemingly)rounded the nut off on it with my o2 socket. It will grip until I apply too much torque to make the socket just spin around the nut. Is the o2 to blame or is something causing the o2 voltage to be so low? I plugged the brake booster line and PCV line and there was no increase in vacuum, should this cause me to think I have a vacuum leak? Still have the scanner so what else should I look for?
EDIT: The 'it' I refer to is the TPS
EDIT: The 'it' I refer to is the TPS
Last edited by PLANT PROTECTION; 02-24-2002 at 04:04 PM.
02-24-2002, 04:57 PM
#34
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too many worries about max tps here-ecm is going to consider most any (depending on the chip)throttle opening above a certain percentage of tps, some chips ive done as low as 60% up to around 80%-im no chip burning pro-not even -but im using the info to illustrate that the ecm will give the motor all its got at any throttle/load above the pre-programmed parameters-meaning wot behavior.max tps is important to an extent but has not much to do with nost all were doing here-yadayada-ok-can you divert air with the scanner in your posession?-if so do it and let it be known what the #'s look like-later p.s. factory fuel pressure is ? on your year? just looked it up-40.5-47 with key on,engine off, 31-42 with engine running. vac. line hooked up-44 was figured at what? betcha its too high
03-04-2002, 11:51 PM
#37
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
There have been subzero temps near me so I haven't been doing much of anything. I hope it warms up to at least 32F or higher in the coming days.
03-05-2002, 03:02 AM
#38
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nooooo thank you-beer stays cold though. from ct. moved to ca. cant say i miss that sh)t
03-05-2002, 10:49 PM
#39
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
I may have added another hurdle that may be skewing my success with my problem. About 3 weeks ago I tried adjusting my minumum air. I interpreted from the tech article leaving the A and B terminals on the ALDL connector grounded throughout the process and I just read a post by Vader making it very clear not to do so. So is my ECM and PROM FKed? How can I tell? I still get changing readings from sensors from my scantool. This brings up another point, after buying my car I found out about my intermittent injector problem. After taking it to a emissions certified mechanic, he stated 6 injectors, ECM, PROM, and cats were shot. He wanted 2Gs to fix so I did the injectors myself and cats at another shop but left the ECM and PROM. Could he have been right, could this be the reason I didn't notice any changed after I grounded it out? Sorry for bringing this up now, I didn't think twice about it before.
03-20-2002, 09:08 PM
#40
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Here's an update guys. I changed my EGR vavle and temp sensor and nothing changed. Another thing I noticed was the AIR pump is always diverting air to the cats and never the manifolds. My o2 volts still drops to 0 whenever I make any kind of acceleration, hard or soft. Could the ECM be hosed?
03-20-2002, 09:37 PM
#41
PP,
I was beginning to wonder if you had given up or finally got it repaired.
If you suspect the ECM, you can do some tests. First, watch the MIL as you turn on the ignition. The light should turn on briefly, then off briefly, then back on and remain on until the engine is running. During this period the ECM does some rudimentart I/O scans for connected hardware, tests the firmware (RAM and PROM checksums), and checks the input and 5VDc voltage supplies. I'm guessing that you are betond this point, since the car runs and you're not generating a code '53' or '55'. You are also establishing diagnostic communication, so it can't be totally fried.
Another thing you can do is to force the backup fuel mode by inserting a 10K resistor in the diagnostic ('B') terminal of the ALDL and grounding the other end (the 'A' terminal is a convenient ECM ground). This should force the ECM to use the backup fuel/spark tables in the PROM, which are typically richer and allow for less advance. This is commonly known as the "Limp Home" mode. Incidentally, a 3.9K resistor in the same terminals will send a request for diagnostic data string dump through the 8192 baud serial terminal on the ALDL, in case you were wondering how you got all that wonderful data through your scan tool.
You can also insert a jumper in the 'A' and 'B' terminals AFTER the engine is running to check the mode and whether the ECM is correcting for a rich or lean condition via the flashes of the MIL lamp.
Of course, all of that data is again available through your scan tool, if you have confidence in it.
For hardware testing, about all you can do is test voltages and check/clean connections. You can test the ECM's 5VDC supply at the TPS sensor. The 'C' (positive) and 'A' (negative) terminals should have 5.0 VDC +/- 0.05V. Of course you can test it directly at the ECM, terminal C14, but the TPS is easier to access.
Another thing you can do is unplug and reconnect the ECM harness connectors several times to clean the connections. The contacts have a wiping action when unplugged. You can also inspect the card edges for corrosion while the connectors are off, and clean any that you may find with a normal pencil eraser.
Beyond that, you could theoretically reseat the CALPAK or remove it and reseat the PROM, just to make sure there is no thermal creep and poor connections as a result. Most of the rest of the components are wave soldered, not socketed, and don't often suffer from connection problems.
If I had a good spare 1227165 I'd offer it, but I only have a few extra CCC and TBI ECMs right now.
I was beginning to wonder if you had given up or finally got it repaired.
If you suspect the ECM, you can do some tests. First, watch the MIL as you turn on the ignition. The light should turn on briefly, then off briefly, then back on and remain on until the engine is running. During this period the ECM does some rudimentart I/O scans for connected hardware, tests the firmware (RAM and PROM checksums), and checks the input and 5VDc voltage supplies. I'm guessing that you are betond this point, since the car runs and you're not generating a code '53' or '55'. You are also establishing diagnostic communication, so it can't be totally fried.
Another thing you can do is to force the backup fuel mode by inserting a 10K resistor in the diagnostic ('B') terminal of the ALDL and grounding the other end (the 'A' terminal is a convenient ECM ground). This should force the ECM to use the backup fuel/spark tables in the PROM, which are typically richer and allow for less advance. This is commonly known as the "Limp Home" mode. Incidentally, a 3.9K resistor in the same terminals will send a request for diagnostic data string dump through the 8192 baud serial terminal on the ALDL, in case you were wondering how you got all that wonderful data through your scan tool.
You can also insert a jumper in the 'A' and 'B' terminals AFTER the engine is running to check the mode and whether the ECM is correcting for a rich or lean condition via the flashes of the MIL lamp.
Of course, all of that data is again available through your scan tool, if you have confidence in it.
For hardware testing, about all you can do is test voltages and check/clean connections. You can test the ECM's 5VDC supply at the TPS sensor. The 'C' (positive) and 'A' (negative) terminals should have 5.0 VDC +/- 0.05V. Of course you can test it directly at the ECM, terminal C14, but the TPS is easier to access.
Another thing you can do is unplug and reconnect the ECM harness connectors several times to clean the connections. The contacts have a wiping action when unplugged. You can also inspect the card edges for corrosion while the connectors are off, and clean any that you may find with a normal pencil eraser.
Beyond that, you could theoretically reseat the CALPAK or remove it and reseat the PROM, just to make sure there is no thermal creep and poor connections as a result. Most of the rest of the components are wave soldered, not socketed, and don't often suffer from connection problems.
If I had a good spare 1227165 I'd offer it, but I only have a few extra CCC and TBI ECMs right now.
03-22-2002, 03:31 AM
#43
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Car: 87 IROC
Engine: LB9 for the moment
Transmission: T5
again just popping in... I'm trying to fix my T/A and outside interference is not helping (work weather no transpo)...
I'll be back...
zroc
I'll be back...
zroc
03-22-2002, 12:46 PM
#44
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
When do I test the 5v ECM from the TPS? I tried it with the igniton on engine off and I got nothing, was this the correct way to test it? I also inserted a 10K resistor in A and B termainals on the ALDL and I noticed no change in performance. I think I should have felt some difference being in limp mode.
03-22-2002, 03:05 PM
#45
Senior Member
put it away
hey all- pickin em up and puttin em down one at a time. scanner tools usually all have within them the feature generically called "divert air" what this lets you do is toggle air injection up or down. so-theres the test for that. no the ecm aint hosed. you gotta remember we are just chasin some stray hc molecules. slow down and put the ecm away. induce a code by pullin the tps or cts while running and if she flashes thats good enough for now. also divert air is an excellent o2 sensor response test watch for voltage changes as you toggle up or down and with that happenning check inj. p width as the ecm responds to lean rich as you trick the o2 sensor. rich=pw decrease lean=pw increase. good enough evidence of a functional ecm. stop touching that ecm do not buy another part till you recieve clearance from HQ. roger that sheeit? over and out, seeya soon
03-22-2002, 11:11 PM
#46
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
Im not 'just' trying to get to the HCs. My car is running and performing much worse than that last emissons test. When my car was running good IMO, I got g-tech times of 6.3 0-60 and 15.0 1/4. I currently get 9.4 0-60 and 17.64 1/4. I would really hate to see current emissions test results. So on my to do list tomorrow:
Divert air and monitor o2 voltage and injector pulse width
EDIT: Here are my numbers although the divert air feature isn't supported by my scantool for my engine.
Open loop:
o2 voltage
idle-.44
wot-.44
injector pulse width
idle-2.3-2.7 varied
wot-bounced from 8.4 to 10.4
Closed loop: (had a hard time staying in closed)
o2 voltage
idle-.6 avg....bounced alot
wot-.1-.2
injector pulse width
idle-2.2
wot-10.6 seemed like it went down as RPM went up tho
Divert air and monitor o2 voltage and injector pulse width
EDIT: Here are my numbers although the divert air feature isn't supported by my scantool for my engine.
Open loop:
o2 voltage
idle-.44
wot-.44
injector pulse width
idle-2.3-2.7 varied
wot-bounced from 8.4 to 10.4
Closed loop: (had a hard time staying in closed)
o2 voltage
idle-.6 avg....bounced alot
wot-.1-.2
injector pulse width
idle-2.2
wot-10.6 seemed like it went down as RPM went up tho
Last edited by PLANT PROTECTION; 03-23-2002 at 05:32 PM.
03-25-2002, 09:34 AM
#47
PP,
Obviously, your ECM is at least working, or you wouldn't be getting that data.
The pulse widths appear to be reacting normally. The injectors will get a longer shot of fuel on hard acceleration until the engine RPM catches up and the load is not as great.
Your O² really doesn't seem odd either. Everything looks right in open-loop, and initially looks good in closed loop (600mV and varying). You're going rich at WOT, which is normal, and all we're not seeing is the data at part-throttle cruise.
And it will normally have some difficulty staying in closed loop when just idling hot since the O² doesn't alway get quite enough exhaust heat to stay at 600°F. Mine changes modes pretty regularly when idling hot.
Your initial post was asking about EGR pulses at idle, and that seems to have been resolved. Since this thread is getting so long that it takes "forever" to load up, you might want to start a different thread with a link to this one for reference.
Obviously, your ECM is at least working, or you wouldn't be getting that data.
The pulse widths appear to be reacting normally. The injectors will get a longer shot of fuel on hard acceleration until the engine RPM catches up and the load is not as great.
Your O² really doesn't seem odd either. Everything looks right in open-loop, and initially looks good in closed loop (600mV and varying). You're going rich at WOT, which is normal, and all we're not seeing is the data at part-throttle cruise.
And it will normally have some difficulty staying in closed loop when just idling hot since the O² doesn't alway get quite enough exhaust heat to stay at 600°F. Mine changes modes pretty regularly when idling hot.
Your initial post was asking about EGR pulses at idle, and that seems to have been resolved. Since this thread is getting so long that it takes "forever" to load up, you might want to start a different thread with a link to this one for reference.
08-25-2002, 09:32 PM
#48
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Car: 1987 Monte Carlo SS
Engine: L98
Transmission: 200-4R
Axle/Gears: 7.625 10 bolt/3.73s
First off I hate bringing up old topics like this but I'm helping people who use the search. My problem was a blown driver's side intake manifold gasket. A clue was my o2s dropping in the .2 range upon acceleration, even WOT indication a very lean conditon. I also noticed my BLMs were at 160 all the time. The thing that tipped me off was oil on the plugs, lots of oil, and I read that a brand new motor had oil on its plugs and a intake gasket was to blame so I said what the hell. It performs and idles good now and my OTC scanner shows EGR position 'off' at idle.
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