Surging/High Idle.... Out of ideas!
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Surging/High Idle.... Out of ideas!
I have an 89 iroc 5.7 TPI, it has an high idle and surging problem. It set for about 10 years and was brought back to life about 6 months ago. In order to get the car running I replaced the fuel tank, fuel pump, and injectors(22lb bosch III's). Since it has been running it has had a high idle and surging. Aside from the idle problems the car runs great and doesn't seem to be lacking any power.
I have replaced and checked:
Plugs and wires (all but 1 plug, i can't get to it)
MAF
IAC (replaced)
TPS
Vacuum leaks several times now with carb cleaner
Replaced some Vac lines that looked old
The car is mostly stock except a few basic things.
Edelbrock A.I.R. headers
Not sure if the CAT is stock or an edelbrock replacement
No muffler (cut off to get gas tank out)
Superchip PROM
3.72 gears
22lb bosch III injectors
Edit:
Update on what else i have done.
Replaced the EGR valve
Rechecked vaccum lines, I removed all the vacuum lines coming out of the plenum and TB one at a time and plugged them with my finger.
I think its running rich which I don't think is a surprise. Could the O2 sensors be causing all of this? I would think I would get a check engine light if they were sending a signal off enough for a high idle.
I have replaced and checked:
Plugs and wires (all but 1 plug, i can't get to it)
MAF
IAC (replaced)
TPS
Vacuum leaks several times now with carb cleaner
Replaced some Vac lines that looked old
The car is mostly stock except a few basic things.
Edelbrock A.I.R. headers
Not sure if the CAT is stock or an edelbrock replacement
No muffler (cut off to get gas tank out)
Superchip PROM
3.72 gears
22lb bosch III injectors
Edit:
Update on what else i have done.
Replaced the EGR valve
Rechecked vaccum lines, I removed all the vacuum lines coming out of the plenum and TB one at a time and plugged them with my finger.
I think its running rich which I don't think is a surprise. Could the O2 sensors be causing all of this? I would think I would get a check engine light if they were sending a signal off enough for a high idle.
Last edited by 89_IROC-Z28; Apr 12, 2010 at 06:29 PM.
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Car: 86 T/A, 83 Z/28
Engine: 5.0 TPI, 350 2 X 4 bbl
Transmission: 4 speed auto, 5 speed manual
Axle/Gears: 3.23 posi, 3.73 std
Re: Surging/High Idle.... Out of ideas!
Check your EGR valve. Its the #1 cause of a surging idle.
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Re: Surging/High Idle.... Out of ideas!
How exactly do i check it? I dont see how i can check it without removing the the plenum (yet again).
Edit: Ok, I should have searched first. Looks like if I remove the vac line from the egr and apply my own vacuum to it, I should notice a change in idle. Is that correct? If so I guess I'm going to have to buy a hand held vac tool.
Last edited by 89_IROC-Z28; Mar 11, 2010 at 10:21 PM.
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Car: 86 T/A, 83 Z/28
Engine: 5.0 TPI, 350 2 X 4 bbl
Transmission: 4 speed auto, 5 speed manual
Axle/Gears: 3.23 posi, 3.73 std
Re: Surging/High Idle.... Out of ideas!
Unfortunately your really cant. What youll want to do is physically remove the EGR valve and made sure the diphram operates freely and its not plugged up with carbon ect. Even vacuum test it if you can but the bottom line is the plenums going to have to come off again unfortunately.
Re: Surging/High Idle.... Out of ideas!
High idle/surging is a tell tale sign of a vacuum leak
When you pull the intake again, double check the mating surfaces are clean as a whistle and use the alignment tabs on the gaskets or a dab of RTV to keep them in position. Dont forget the TB gasket too
EVAP line on the TB is big enough to really mess up idle, and the rubber hose is surely deteriorated by now, also check for cracks in the booster line
When you pull the intake again, double check the mating surfaces are clean as a whistle and use the alignment tabs on the gaskets or a dab of RTV to keep them in position. Dont forget the TB gasket too
EVAP line on the TB is big enough to really mess up idle, and the rubber hose is surely deteriorated by now, also check for cracks in the booster line
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Re: Surging/High Idle.... Out of ideas!
High idle/surging is a tell tale sign of a vacuum leak
When you pull the intake again, double check the mating surfaces are clean as a whistle and use the alignment tabs on the gaskets or a dab of RTV to keep them in position. Dont forget the TB gasket too
EVAP line on the TB is big enough to really mess up idle, and the rubber hose is surely deteriorated by now, also check for cracks in the booster line
When you pull the intake again, double check the mating surfaces are clean as a whistle and use the alignment tabs on the gaskets or a dab of RTV to keep them in position. Dont forget the TB gasket too
EVAP line on the TB is big enough to really mess up idle, and the rubber hose is surely deteriorated by now, also check for cracks in the booster line
I havent checked the egr yet but was looking at the evap lines. I noticed that the vac. line coming from the charcoal canister was going to the heater valve, and the vac. line coming from the firewall for the HVAC was going to the charcoal canister. I switched them and it caused the surging to get alot worse and the idle to be a little ruff. I remember i swapped them once before but put them back because of this.
You think the evap system is where my problem is and switching those vac lines is just magnifying it?
Also, the IAC seems to be opening and closing alot. It stays open most the time and i can hear the air sucking though. When the idle actually goes down (does once in a wile) I cant hear the sucking sound from the IAC anymore.
Last edited by 89_IROC-Z28; Mar 12, 2010 at 02:52 PM.
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Re: Surging/High Idle.... Out of ideas!
Ok, I have found out that the charcoal canister is sucking air from the vent on top of it. If i put my finder over the vent then the canister its self will start to crush. If I unplug the vac line going to the canister at the TB and cover the hole on the TB then the surging goes away. The vac line between the TB and canister is good, and I changed the other vac lines coming from the canister that were bad a wile back. Whats up with the charcoal canister leaking vacuum out of its vent?
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Re: Surging/High Idle.... Out of ideas!
A faulty IAC will screw with idle, but usually when its bad it doesnt move at all
Cap the vacuum ports and see if the idle comes back to normal
Cap the vacuum ports and see if the idle comes back to normal
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Re: Surging/High Idle.... Out of ideas!
Well I capped the port and the idle came down. It still has a very slight surge to it but if it will stay like it is now I'm fine with it. It almost seems like its idled down to much once I put it into gear. Then again maby it isnt, I dont have an accurate rpm gauge to tell me for sure.
I replaced the IAC so it its self shouldn't be bad.
Now the question is, what do i do about the charcoal canister? I cant just leave the vac line laying there and the port on the TB capped off, can I? I dont car about passing emissions if that would be the only reason.
I replaced the IAC so it its self shouldn't be bad.
Now the question is, what do i do about the charcoal canister? I cant just leave the vac line laying there and the port on the TB capped off, can I? I dont car about passing emissions if that would be the only reason.
Last edited by 89_IROC-Z28; Mar 12, 2010 at 06:15 PM.
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Re: Surging/High Idle.... Out of ideas!
I had it idling for a wile to see how it ran as it got to operating temp. and the high idle came back. I took it for a drive and did some WOT runs along with just cruising, it idled back down after about 5-10mins of driving around.
Last edited by 89_IROC-Z28; Mar 12, 2010 at 10:02 PM.
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Re: Surging/High Idle.... Out of ideas!
Ok update,
I had time to take the plenum off today and look at the egr valve. I can't seem to get the back bolt on the egr valve off. I cant get anything to fit right on the bolt with the tiny amount of room in there. I have tried everything I can think of and the bolt is beginning to get stripped out. Wile the egr was still on the car I tried pulling diaphragm up and covering the vac. port with my finger. It would not hold vacuum, so I am thinking Rollling Thunder is correct.
Anybody that has removed an EGR valve, how did you get the back bolt off?
Before I took the plenum off I put a gauge on the vacuum line going to the egr, and I was getting a good vacuum. I then tried to put a constant vacuum on the egr valve and noticed no change in idle, and could not feel the diaphragm in the egr move.
Ohh and this happened to the egr temp sensor....
I am going to try to solder it back together. It looks like it was soldered on once before.
I had time to take the plenum off today and look at the egr valve. I can't seem to get the back bolt on the egr valve off. I cant get anything to fit right on the bolt with the tiny amount of room in there. I have tried everything I can think of and the bolt is beginning to get stripped out. Wile the egr was still on the car I tried pulling diaphragm up and covering the vac. port with my finger. It would not hold vacuum, so I am thinking Rollling Thunder is correct.
Anybody that has removed an EGR valve, how did you get the back bolt off?
Before I took the plenum off I put a gauge on the vacuum line going to the egr, and I was getting a good vacuum. I then tried to put a constant vacuum on the egr valve and noticed no change in idle, and could not feel the diaphragm in the egr move.
Ohh and this happened to the egr temp sensor....
I am going to try to solder it back together. It looks like it was soldered on once before.
Last edited by 89_IROC-Z28; Mar 15, 2010 at 11:23 PM.
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Car: 86 T/A, 83 Z/28
Engine: 5.0 TPI, 350 2 X 4 bbl
Transmission: 4 speed auto, 5 speed manual
Axle/Gears: 3.23 posi, 3.73 std
Re: Surging/High Idle.... Out of ideas!
I recomend lots of penetrating oil (I like PB blaster) and a good short wrench (maybe even a few taps with a hammer if you can fit it). Its a tight fit and they can be very stubborn but it can be done. The important thing is not to strip it. Maybe some heat would be in order but it does sound like you may have found your issue (or at least 1 problem) assuming its an original negative type EGR valve.
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Car: Trailblazer EXT 4.2 (Firebird Form)
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Re: Surging/High Idle.... Out of ideas!
I think I used this type of wrench when I changed my egr, can't remember what else I would have used it for...
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Axle/Gears: 2.73
Re: Surging/High Idle.... Out of ideas!
once you get it out make sure you spray some carb cleaner (I don't think it will harm anything in there) or some TB cleaner into the ports... on mine when I did it, it was full of soot... took about 3/4 of a can of carb cleaner to get it flowing into the combustion chambers...
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Re: Surging/High Idle.... Out of ideas!
I recomend lots of penetrating oil (I like PB blaster) and a good short wrench (maybe even a few taps with a hammer if you can fit it). Its a tight fit and they can be very stubborn but it can be done. The important thing is not to strip it. Maybe some heat would be in order but it does sound like you may have found your issue (or at least 1 problem) assuming its an original negative type EGR valve.
As far as I know it is the original. I did forget to check if it was a negative or positive.
I'm going to go soak it in PB blaster right now. Maby it will be a little loosened up by morning.
once you get it out make sure you spray some carb cleaner (I don't think it will harm anything in there) or some TB cleaner into the ports... on mine when I did it, it was full of soot... took about 3/4 of a can of carb cleaner to get it flowing into the combustion chambers...
Last edited by 89_IROC-Z28; Mar 15, 2010 at 11:45 PM.
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Re: Surging/High Idle.... Out of ideas!
If it looks original it probably is or its at least old enough so that it would have been replaced with a negative type EGR valve as it wasn't all that long ago manufacturers switched over to positive type EGR replacements for our cars. Course its not to bad to tell if its negative or positive type EGR valve depending on brand and either way even if it was a positive type EGR it still has to come of for inspection so no big deal.
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Re: Surging/High Idle.... Out of ideas!
Okay, I got busy and haven't worked on the car much.
I changed the EGR valve and it didn't seem to effect it any.
Today I took the car to a local shop to get a smoke test on the vac. system. It was going to cost $50 so i decided against it. Wile there they looked over the motor well and tried spraying ether or starting fluid (something like that) around the motor and didn't find anything. I have done the same before and got the same results.
What do you guys think?
I changed the EGR valve and it didn't seem to effect it any.
Today I took the car to a local shop to get a smoke test on the vac. system. It was going to cost $50 so i decided against it. Wile there they looked over the motor well and tried spraying ether or starting fluid (something like that) around the motor and didn't find anything. I have done the same before and got the same results.
What do you guys think?
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Re: Surging/High Idle.... Out of ideas!
I have a similar problem right now with my 89 Formula. 305 TPI, and had it with my 89 Iroc, also 305 TPI.
I blocked off the egr valve with a steel plate in the Camaro, and it solved the problem of it dying on my after warming up.
As for the firebird, I'm not really sure whats causing it. It was running fine for a year strait, then just the other day in traffic, I got a check engine light and started over heating. After pulling over and cooling down I set off and had no issues until almost a day later. It started bucking on me while at constant throttle with no check engine light. Parked the car, now it won't start.
I got it started 3 times since: it idles real low, in the 500 range, then craps out. Runs rough as hell if I try to give it any throttle.
My shorthand list of things to check: (some more connected to the issue than others)
EGR valve
Plugs/wire
Idle Air Control Valve
Throttle position sensor
Distributor module/cap/rotor
Fuel pump relay
Fuel pressure regulator
Fuel pressue
@ idle
@ idle with fuel pressure regulator vaccum line off
@ WOT in 2nd gear
Vacuum lines.
Do you get any check engine lights?
I blocked off the egr valve with a steel plate in the Camaro, and it solved the problem of it dying on my after warming up.
As for the firebird, I'm not really sure whats causing it. It was running fine for a year strait, then just the other day in traffic, I got a check engine light and started over heating. After pulling over and cooling down I set off and had no issues until almost a day later. It started bucking on me while at constant throttle with no check engine light. Parked the car, now it won't start.
I got it started 3 times since: it idles real low, in the 500 range, then craps out. Runs rough as hell if I try to give it any throttle.
My shorthand list of things to check: (some more connected to the issue than others)
EGR valve
Plugs/wire
Idle Air Control Valve
Throttle position sensor
Distributor module/cap/rotor
Fuel pump relay
Fuel pressure regulator
Fuel pressue
@ idle
@ idle with fuel pressure regulator vaccum line off
@ WOT in 2nd gear
Vacuum lines.
Do you get any check engine lights?
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Re: Surging/High Idle.... Out of ideas!
I have a similar problem right now with my 89 Formula. 305 TPI, and had it with my 89 Iroc, also 305 TPI.
I blocked off the egr valve with a steel plate in the Camaro, and it solved the problem of it dying on my after warming up.
As for the firebird, I'm not really sure whats causing it. It was running fine for a year strait, then just the other day in traffic, I got a check engine light and started over heating. After pulling over and cooling down I set off and had no issues until almost a day later. It started bucking on me while at constant throttle with no check engine light. Parked the car, now it won't start.
I got it started 3 times since: it idles real low, in the 500 range, then craps out. Runs rough as hell if I try to give it any throttle.
My shorthand list of things to check: (some more connected to the issue than others)
EGR valve
Plugs/wire
Idle Air Control Valve
Throttle position sensor
Distributor module/cap/rotor
Fuel pump relay
Fuel pressure regulator
Fuel pressue
@ idle
@ idle with fuel pressure regulator vaccum line off
@ WOT in 2nd gear
Vacuum lines.
Do you get any check engine lights?
I blocked off the egr valve with a steel plate in the Camaro, and it solved the problem of it dying on my after warming up.
As for the firebird, I'm not really sure whats causing it. It was running fine for a year strait, then just the other day in traffic, I got a check engine light and started over heating. After pulling over and cooling down I set off and had no issues until almost a day later. It started bucking on me while at constant throttle with no check engine light. Parked the car, now it won't start.
I got it started 3 times since: it idles real low, in the 500 range, then craps out. Runs rough as hell if I try to give it any throttle.
My shorthand list of things to check: (some more connected to the issue than others)
EGR valve
Plugs/wire
Idle Air Control Valve
Throttle position sensor
Distributor module/cap/rotor
Fuel pump relay
Fuel pressure regulator
Fuel pressue
@ idle
@ idle with fuel pressure regulator vaccum line off
@ WOT in 2nd gear
Vacuum lines.
Do you get any check engine lights?
Well I think I am having the opposite problem. I have a high idle, surging and no check engine light.
One think you might want to check is the MAF sensor. Just unplug it and see if it runs any better.
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Re: Surging/High Idle.... Out of ideas!
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Re: Surging/High Idle.... Out of ideas!
Aah okay, maby what ever the problem part is just hasn't completely failed on my car yet. If you do figure out what the problem is please let me know.
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Re: Surging/High Idle.... Out of ideas!
I found a diagram but lost the page. Saved me some time finding it again, thanks.
One thing that diagram reminded me of is the EGR solenoid. Anybody have any idea how i would go about testing it?
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Re: Surging/High Idle.... Out of ideas!
Vaccum line diagram for 90 firebird by any chance??? Sorry to hack thread <---nevermind plenty of diagrams on site
Last edited by maks10; Apr 8, 2010 at 10:29 PM.
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Re: Surging/High Idle.... Out of ideas!
Bump
Something i dont think i said in my other posts. If I rev the motor up once without letting the it idle or driving the car for a couple minutes then it will die. Today i drove it and I had to set in traffic for a couple minuets. I started to smell gas, this just confirms its running rich.
Could a bad O2 sensor cause all of this? I should be getting a check engine light if its reading off enough to cause a high idle though.
Something i dont think i said in my other posts. If I rev the motor up once without letting the it idle or driving the car for a couple minutes then it will die. Today i drove it and I had to set in traffic for a couple minuets. I started to smell gas, this just confirms its running rich.
Could a bad O2 sensor cause all of this? I should be getting a check engine light if its reading off enough to cause a high idle though.
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Re: Surging/High Idle.... Out of ideas!
I just fixed(10 min ago) my high and climbing idle and surge issue with copious amounts of throttle body cleaner, vacuum ports were nasty as was the IAC port, it was $3 for the can and 10 min off intermittent spraying. best wishes, Johnny Rocco
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Re: Surging/High Idle.... Out of ideas!
I tried unplugging the O2 sensor and it ran a little worse but didnt throw the check engine light on for some reason. I let it idle with some revving for 10 minuets.
I removed and clean the passage out for the IAC but I have already cleaned the throttle body once so it was clean.
Anybody else have any idea what could be going on here?
I removed and clean the passage out for the IAC but I have already cleaned the throttle body once so it was clean.
Anybody else have any idea what could be going on here?
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Re: Surging/High Idle.... Out of ideas!
A bad 02 doesn't always set a code. The only way I found the one on my 86 had failed was to monitor it using Diacom and found it wasn't cycling as it should.
Same thing with a bad MAF. No code but it had a broken wire.
Surging most often means a lean condition many times caused by a vacuum leak. Some leaks are really hard to detect. I recall having to just about flood the engine suspect areas with my garden hose water to find the vacuum leak at one of the injector "O" rings. Spray carb cleaner didn't get it done; water did though.
After all you've been through, you're at the point of needing a real time scanner to monitor the sensor readings.
Have you attached a vacuum gage to the idling engine? If so, what was the reading; was it steady?
Jake
Same thing with a bad MAF. No code but it had a broken wire.
Surging most often means a lean condition many times caused by a vacuum leak. Some leaks are really hard to detect. I recall having to just about flood the engine suspect areas with my garden hose water to find the vacuum leak at one of the injector "O" rings. Spray carb cleaner didn't get it done; water did though.
After all you've been through, you're at the point of needing a real time scanner to monitor the sensor readings.
Have you attached a vacuum gage to the idling engine? If so, what was the reading; was it steady?
Jake
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Re: Surging/High Idle.... Out of ideas!
Well I did a wile back but forgot the number so i ran out and tested it. The car was surging alot, but i got 17" durring the lowest idle of the surge and 20" during the highest rpm. When the car is idling high with little to no surge its at 20".
I did find that plugging the line from the charcoal canister going to the TB causes the car to surge less. Also is the charcoal canister suppose to be sucking alot of air in the vent on top of it?
I did find that plugging the line from the charcoal canister going to the TB causes the car to surge less. Also is the charcoal canister suppose to be sucking alot of air in the vent on top of it?
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Re: Surging/High Idle.... Out of ideas!
I still believe you engine has a vacuum leak. I've had my best luck finding a vacuum leak using water from my garden hose. I watch to prevent splashing or to prevent flooding sensors but I use MORE water rather than less.
Jake
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Re: Surging/High Idle.... Out of ideas!
". . . sucking a lot of air . . ." No, it shouldn't. That needs sealing.
I still believe you engine has a vacuum leak. I've had my best luck finding a vacuum leak using water from my garden hose. I watch to prevent splashing or to prevent flooding sensors but I use MORE water rather than less.
Jake
I still believe you engine has a vacuum leak. I've had my best luck finding a vacuum leak using water from my garden hose. I watch to prevent splashing or to prevent flooding sensors but I use MORE water rather than less.
Jake
The water deal scares me. You just hold the water hose around and under the plenum, and vacuum lines? How much water we talking here, like a full stream or just like a water faucet in the bathroom?
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Re: Surging/High Idle.... Out of ideas!
You don't want pressure like a fire hose putting out a fire. No need to direct water at sensors/senders that screw into coolant ports. No need to direct water at purely electrical sensors/connectors. Only areas where there's vacuum.
Here are some more ideas:
Disconnect and plug the cannister vacuum source, both ends of the hose. Fuel pressure vacuum hose; where hose bibs screw into the intake, injector "O" ring locations, intake manifold bolt locations, sources upstream of the MAF/MAP. Exhaust leak before the 02 (s).
You should also connect a scanner to check for the sensor read-outs to see if one or more is operating out of range. 02 and Coolant Temp Sensor malfunctions can cause idle and running problems.
Throttle body leaking vacuum; gasket/shaft? Hole/tear in the accordion?
Have you fooled with the valve train lately? Lifter preload set too tightly??
Jake
Here are some more ideas:
Disconnect and plug the cannister vacuum source, both ends of the hose. Fuel pressure vacuum hose; where hose bibs screw into the intake, injector "O" ring locations, intake manifold bolt locations, sources upstream of the MAF/MAP. Exhaust leak before the 02 (s).
You should also connect a scanner to check for the sensor read-outs to see if one or more is operating out of range. 02 and Coolant Temp Sensor malfunctions can cause idle and running problems.
Throttle body leaking vacuum; gasket/shaft? Hole/tear in the accordion?
Have you fooled with the valve train lately? Lifter preload set too tightly??
Jake
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Re: Surging/High Idle.... Out of ideas!
You don't want pressure like a fire hose putting out a fire. No need to direct water at sensors/senders that screw into coolant ports. No need to direct water at purely electrical sensors/connectors. Only areas where there's vacuum.
Here are some more ideas:
Disconnect and plug the cannister vacuum source, both ends of the hose. Fuel pressure vacuum hose; where hose bibs screw into the intake, injector "O" ring locations, intake manifold bolt locations, sources upstream of the MAF/MAP. Exhaust leak before the 02 (s).
You should also connect a scanner to check for the sensor read-outs to see if one or more is operating out of range. 02 and Coolant Temp Sensor malfunctions can cause idle and running problems.
Throttle body leaking vacuum; gasket/shaft? Hole/tear in the accordion?
Have you fooled with the valve train lately? Lifter preload set too tightly??
Jake
Here are some more ideas:
Disconnect and plug the cannister vacuum source, both ends of the hose. Fuel pressure vacuum hose; where hose bibs screw into the intake, injector "O" ring locations, intake manifold bolt locations, sources upstream of the MAF/MAP. Exhaust leak before the 02 (s).
You should also connect a scanner to check for the sensor read-outs to see if one or more is operating out of range. 02 and Coolant Temp Sensor malfunctions can cause idle and running problems.
Throttle body leaking vacuum; gasket/shaft? Hole/tear in the accordion?
Have you fooled with the valve train lately? Lifter preload set too tightly??
Jake
I have disconnected each vacuum line from the plenum/TB one at a time and plugged them. I disconnected one plugged it at the plenum/TB and then reconnected it, then disconnected another and plugged it, etc.... So I should have eliminated all the vacuum lines and canister that way correct?
I am not sure what you mean by "Fuel pressure vacuum hose; where hose bibs screw into the intake".
Injector "O" rings are all new and have been sprayed with CC but may I hit them with water when i do that. Same for the intake manifold bolts.
MAF and the accordion boot are sealed well with no rips. TB has a new gasket between it and the plenum, and everything on it sprayed with CC, didnt find any leaks.
Exhaust does have several leaks, they are all after the O2 sensor, but before the cat. I only found one O2 in the drivers side collector, could not find one on the passenger side anywhere.
I do know the coolant temp sensor on the passenger side of the block may be bad. The wire and connector was melted by the header. I repaired the wire but the connector is still melted. I far as I can tell though that is just the temp switch for the e-fans.
I have not messed with the valve train or anything internal. I do not have a scanner or any shops around that has one that will work. I live in a small town so not many shops. I did look into buying a cable and downloading a some free software but just got confused and overwhelmed with all the info.
Thanks for all the help by the way.
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From: Kempner,TX,
Car: 1996 Vette / 1992 GSX1100F Suzuki
Engine: 1996 Corvette Coupe 388 LT1 (+.060)
Transmission: Auto
Axle/Gears: 3.07
Re: Surging/High Idle.... Out of ideas!
I have disconnected each vacuum line from the plenum/TB one at a time and plugged them. I disconnected one plugged it at the plenum/TB and then reconnected it, then disconnected another and plugged it, etc.... So I should have eliminated all the vacuum lines and canister that way correct? No, you should disconnect and plug all the vacuum sources, all at the same time. Idle the engine, and as it idles re-connect the vacuum connections one at a time. The connection that negatively effects the idle is the culprit.
I am not sure what you mean by "Fuel pressure vacuum hose; where hose bibs screw into the intake". Part of the problem for me is I've never worked on a 90-92 Only 86 and 96s. On those two engines, 86 and 96, the Fuel Pressure Regulator has a vacuum hose that runs from the FPR to the plenum. At the plenum there is a fitting sometimes referred to as a "hose bib" screwed into the plenum. The bib itself could leak vacuum. The plenum supplies vacuum so that the fuel pressure increases as vacuum drops.
Injector "O" rings are all new and have been sprayed with CC but may I hit them with water when i do that. Same for the intake manifold bolts.
MAF and the accordion boot are sealed well with no rips. TB has a new gasket between it and the plenum, and everything on it sprayed with CC, didnt find any leaks.
Exhaust does have several leaks, they are all after the O2 sensor, but before the cat. I only found one O2 in the drivers side collector, could not find one on the passenger side anywhere. A scanner can show you if any of those leaks are effecting the proper operation of the 02 sensor. A Digital Volt Meter can be used to check the 02 for proper operation but I've never done it that way so I can't post the procedure or what readings to look for. Maybe someone else will chime in with that.
I do know the coolant temp sensor on the passenger side of the block may be bad. The wire and connector was melted by the header. I repaired the wire but the connector is still melted. I far as I can tell though that is just the temp switch for the e-fans. On the 86 the Coolant Temperature Sensor is screwed into the passenger side front of the intake manifold. It's an important sensor used by the ECM to determine correct fuel delivery and spark timing, etc.
I have not messed with the valve train or anything internal. I do not have a scanner or any shops around that has one that will work. I live in a small town so not many shops. I did look into buying a cable and downloading a some free software but just got confused and overwhelmed with all the info.
Thanks for all the help by the way.
I am not sure what you mean by "Fuel pressure vacuum hose; where hose bibs screw into the intake". Part of the problem for me is I've never worked on a 90-92 Only 86 and 96s. On those two engines, 86 and 96, the Fuel Pressure Regulator has a vacuum hose that runs from the FPR to the plenum. At the plenum there is a fitting sometimes referred to as a "hose bib" screwed into the plenum. The bib itself could leak vacuum. The plenum supplies vacuum so that the fuel pressure increases as vacuum drops.
Injector "O" rings are all new and have been sprayed with CC but may I hit them with water when i do that. Same for the intake manifold bolts.
MAF and the accordion boot are sealed well with no rips. TB has a new gasket between it and the plenum, and everything on it sprayed with CC, didnt find any leaks.
Exhaust does have several leaks, they are all after the O2 sensor, but before the cat. I only found one O2 in the drivers side collector, could not find one on the passenger side anywhere. A scanner can show you if any of those leaks are effecting the proper operation of the 02 sensor. A Digital Volt Meter can be used to check the 02 for proper operation but I've never done it that way so I can't post the procedure or what readings to look for. Maybe someone else will chime in with that.
I do know the coolant temp sensor on the passenger side of the block may be bad. The wire and connector was melted by the header. I repaired the wire but the connector is still melted. I far as I can tell though that is just the temp switch for the e-fans. On the 86 the Coolant Temperature Sensor is screwed into the passenger side front of the intake manifold. It's an important sensor used by the ECM to determine correct fuel delivery and spark timing, etc.
I have not messed with the valve train or anything internal. I do not have a scanner or any shops around that has one that will work. I live in a small town so not many shops. I did look into buying a cable and downloading a some free software but just got confused and overwhelmed with all the info.
Thanks for all the help by the way.
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Re: Surging/High Idle.... Out of ideas!
No, you should disconnect and plug all the vacuum sources, all at the same time. Idle the engine, and as it idles re-connect the vacuum connections one at a time. The connection that negatively effects the idle is the culprit.
I will have to buy a pack of various sized vacuum caps and try that.
Part of the problem for me is I've never worked on a 90-92 Only 86 and 96s. On those two engines, 86 and 96, the Fuel Pressure Regulator has a vacuum hose that runs from the FPR to the plenum. At the plenum there is a fitting sometimes referred to as a "hose bib" screwed into the plenum. The bib itself could leak vacuum. The plenum supplies vacuum so that the fuel pressure increases as vacuum drops.
Well the car is an 89 that should be original other then the mods listed in my original post. For some reason I have the 90-92 style charcoal canister though. I know what your talking about with the FPR vac. hose now though. I must have had a brain fart.
I do know the vac. line its self is fine, but did not check the bib. I didnt even know they screwed out, I thought they were pressed in.
A scanner can show you if any of those leaks are effecting the proper operation of the 02 sensor. A Digital Volt Meter can be used to check the 02 for proper operation but I've never done it that way so I can't post the procedure or what readings to look for. Maybe someone else will chime in with that.
I will do some searching on that, maby there is a thread describing how to check it with a volt meter. Would be nice if someone would chime in and save me more searching though.
On the 86 the Coolant Temperature Sensor is screwed into the passenger side front of the intake manifold. It's an important sensor used by the ECM to determine correct fuel delivery and spark timing, etc.
I know exactly where that is and it looks to be in good shape. Of course I cant tell if it is internally ok. I will see if I can find out how to test that also.
I will have to buy a pack of various sized vacuum caps and try that.
Part of the problem for me is I've never worked on a 90-92 Only 86 and 96s. On those two engines, 86 and 96, the Fuel Pressure Regulator has a vacuum hose that runs from the FPR to the plenum. At the plenum there is a fitting sometimes referred to as a "hose bib" screwed into the plenum. The bib itself could leak vacuum. The plenum supplies vacuum so that the fuel pressure increases as vacuum drops.
Well the car is an 89 that should be original other then the mods listed in my original post. For some reason I have the 90-92 style charcoal canister though. I know what your talking about with the FPR vac. hose now though. I must have had a brain fart.
I do know the vac. line its self is fine, but did not check the bib. I didnt even know they screwed out, I thought they were pressed in.A scanner can show you if any of those leaks are effecting the proper operation of the 02 sensor. A Digital Volt Meter can be used to check the 02 for proper operation but I've never done it that way so I can't post the procedure or what readings to look for. Maybe someone else will chime in with that.
I will do some searching on that, maby there is a thread describing how to check it with a volt meter. Would be nice if someone would chime in and save me more searching though.
On the 86 the Coolant Temperature Sensor is screwed into the passenger side front of the intake manifold. It's an important sensor used by the ECM to determine correct fuel delivery and spark timing, etc.
I know exactly where that is and it looks to be in good shape. Of course I cant tell if it is internally ok. I will see if I can find out how to test that also.
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Re: Surging/High Idle.... Out of ideas!
Well, I caped off all the vacuum lines and there was no difference. I connected the FPR, and brake booster back. Then I connected the EGR valve to a constant vacuum bypassing the solenoid, and the car idled down and didnt surge or anything. It was just like its suppose to be other then a very slight stumble at idle, but the car ran great.
Now the question...
Isnt the EGR valve not suppose to have vacuum until around 2k rpm? Why would me applying vacuum fix my idle problem? It is the newer positive type valve if that matters.
Now the question...
Isnt the EGR valve not suppose to have vacuum until around 2k rpm? Why would me applying vacuum fix my idle problem? It is the newer positive type valve if that matters.
Last edited by 89_IROC-Z28; Apr 25, 2010 at 05:37 PM.
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From: Kempner,TX,
Car: 1996 Vette / 1992 GSX1100F Suzuki
Engine: 1996 Corvette Coupe 388 LT1 (+.060)
Transmission: Auto
Axle/Gears: 3.07
Re: Surging/High Idle.... Out of ideas!
You're going to have to refer to your year specific Service Manual for the correct type of EGR valve your engine requires. There are three different types; Positive, Negative and Ported (Port) Valve.
The one specified in my 86 Corvette Factory Service Manuals says my formed 86 L98 engine calls for a negative backpressure valve. Page 6E3-C7-1, lower right paragraph on the page. Each is identified by the letter "P", "N" or no identification stamped on the EGR valve after the part number.
Here is some information take from my 86 FSM:
"Too much EGR flow at idle, cruise or cold operation causes:
Engine to stall after start up
Engine stops at idle after deceleration
Care surges during cruise
Rough idle
Other problems occur when the EGR stays open all of the time and the engine may not run.
Too little or no EGR flow allows combustion chamber temperatures to be too high during acceleration and load conditions which could cause:
Spark knock (detonation)
Engine over-heating
Emission test failure
To more closely regulate EGR flow, an ECM controlled solenoid is used in the vacuum line."
On the 86, the ECM uses four sensor inputs to regulate the EGR solenoid. You'll have to check your FSM for your specific year trouble-shooting procedures.
Jake
The one specified in my 86 Corvette Factory Service Manuals says my formed 86 L98 engine calls for a negative backpressure valve. Page 6E3-C7-1, lower right paragraph on the page. Each is identified by the letter "P", "N" or no identification stamped on the EGR valve after the part number.
Here is some information take from my 86 FSM:
"Too much EGR flow at idle, cruise or cold operation causes:
Engine to stall after start up
Engine stops at idle after deceleration
Care surges during cruise
Rough idle
Other problems occur when the EGR stays open all of the time and the engine may not run.
Too little or no EGR flow allows combustion chamber temperatures to be too high during acceleration and load conditions which could cause:
Spark knock (detonation)
Engine over-heating
Emission test failure
To more closely regulate EGR flow, an ECM controlled solenoid is used in the vacuum line."
On the 86, the ECM uses four sensor inputs to regulate the EGR solenoid. You'll have to check your FSM for your specific year trouble-shooting procedures.
Jake
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Re: Surging/High Idle.... Out of ideas!
See the thing is I have non of that with a constant vacuum on the EGR. I may have had a slight power decrease but it could just be me, or the car not running a little rich like it was.
Anybody else have any ideas about my EGR valve? I have driven the car more the past 3 days then it gets driven in 3 weeks. Its been running great everyday too.
Anybody else have any ideas about my EGR valve? I have driven the car more the past 3 days then it gets driven in 3 weeks. Its been running great everyday too.
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Re: Surging/High Idle.... Out of ideas!
Please explain, I have never heard of that. I dont see anyway low coolant could cause high idle. I know the coolant is full, I check all the fluids often. I also just flushed it and refilled it because it was nasty looking.
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From: San Diego, California
Car: Trailblazer EXT 4.2 (Firebird Form)
Engine: 5.1 4bbl
Transmission: 700R4 Mega Raptor Level 4
Axle/Gears: 2.73
Re: Surging/High Idle.... Out of ideas!
probably the coolant temperature sensor not getting an accurate reading would instruct the ECM that the car was still running cold... that's just my theory though...
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Car: 1986 IROC
Engine: 305 TPI
Transmission: 700R4
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Re: Surging/High Idle.... Out of ideas!
I can see that, but I would think after the motor was up to temp. it would read close enough to fix that problem. Seems like the motor would actually run a little warm after a wile from lack of coolant.
Anybody have any other ideas? Constant vacuum to the EGR cant be right, but its lowered me idle down.
Anybody have any other ideas? Constant vacuum to the EGR cant be right, but its lowered me idle down.
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Joined: Feb 2010
Posts: 1,125
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From: San Diego, California
Car: Trailblazer EXT 4.2 (Firebird Form)
Engine: 5.1 4bbl
Transmission: 700R4 Mega Raptor Level 4
Axle/Gears: 2.73
Re: Surging/High Idle.... Out of ideas!
Coolant, ummm.. coolant is the means of transferring heat from point A (engine) to point B (radiator) ... if there isn't the amount of coolant that a temp sensor requires to get an accurate reading, then how is it going to determine the vehicle is hot... there isn't another temp sensor in the oil... or anywhere else, at least not in our 3rd gens....
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Re: Surging/High Idle.... Out of ideas!
I guess your thinking alot lower coolant than I am. I would also think conduction from the intake manifold would heat the senor some what, and that combined with the small amount of coolant in the system would heat it enough to go into closed loop once the motor got up to operating temp.
Either way, I have good coolant and the level is good so that cant be it. The sensor could be bad though. I haven't had time to check it since I have been focusing on the EGR.
Either way, I have good coolant and the level is good so that cant be it. The sensor could be bad though. I haven't had time to check it since I have been focusing on the EGR.
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From: San Diego, California
Car: Trailblazer EXT 4.2 (Firebird Form)
Engine: 5.1 4bbl
Transmission: 700R4 Mega Raptor Level 4
Axle/Gears: 2.73
Re: Surging/High Idle.... Out of ideas!
The EGR I believe will make the car stumble when tapping the gas...
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Re: Surging/High Idle.... Out of ideas!
It runs perfectly fine except for a slight stumble or miss at idle. When i hit the gas it takes off great like it should. I will try tapping the gas and see if it causes a stumble. I know if I taped it once quickly before I messed with the EGR it would sometimes die if i didnt give it a little gas.