I'm trying to solve this on my own. Here's what was replaced 2 yrs ago, and we've only driven 8,000 miles since then.

TPI 305/auto, 138k - only mods are K&N's and an Edelbrock cat-back
Plugs, wires, cap, rotor
O2 sensor
Cat converter

Since some point last year, the SES light comes on for insufficient EGR flow, but its never affected the car's driving. In the last couple months, sporadically, the car has ran like crap. I drove it Monday/Tuesday, and it was fine. Wednesday and Friday it was a total dog. So rich it burned the eyes and would barely idle or drive at any speed.

I did a few runs with Datamaster and have some data if someone would like to see it. The EGR code is still there, but not too much else. The TPS was up around .67v, so I adjusted it to .55. The MAP sensor is reading between 40-55 at idle, which seems high, and explains why its in fuel cell 4 instead of 1 at idle. On Monday and Tuesday, everything seemed fine (not the smoothest idle like it used to, but perfectly driveable). Friday when it is running like garbage, the O2 mvolts were above 800 at idle (in closed loop), with no cross counts. Once I start driving a little it started bouncing above/below but still bogs big time. After this is also set a rich exhaust code (duh). BLMs also drop to around 108 frequently, and I think dropped into the 90's at some point.

I tested for vacuum leaks (soapy water, propane), and couldn't find anything. I also swapped the plugs again and no change. It sucks to drive and our emissions is due next month. I can't think of anything that wouldn't affect the car all of the time? Is there a way to test for a fuel injector hanging open? I tried to listen and they seemed fine. I'm thinking it must be something on the drivers side since the O2 sensor is seeing the rich condition?

PLEASE, any thoughts welcome.

 

how did you adjust your TPS? I could be wrong but I thought SD systems didn't have an adjustable TPS

 

The way the tech article on here says to - loosen the screws, move up/down until its approximately .54v on the scan tool, then tighten.

 

You might want to check your coolant temp sensor; the resistance values are in the 4th or 5th post

https://www.thirdgen.org/forums/elec...cts+resistance

 

I'll check into it. The engine temp that shows up in Datamaster I think comes from the ECM/thermostat area. The temps are reasonable and close to the autometer gauge connected to the sender in the DS head but its worth a shot.

Keep 'em coming!

 

Checks CTS and all injectors, no problems.

Any other thoughts???

 

O2 Might be bad since your not getting crosscounts. Also check vac line to MAP, check/replace CTS, also check injector harness to be sure injectors are not being grounded out.

 

Pull the vacuum line off the fuel pressure regulator and see if any gas comes out???

 

On the O2, I do get cross counts during driving, just not at idle. It is also reading as I would expect (rich), so I'm hesitant to switch it at 8,000 miles for "nothing". Vac line to the MAP checks out, and I have checked the CTS. Although I checked the injector's, I didn't check the harness. Can I do this with the engine off and key on, i.e. will they still pulse?

I will check the regulator line, and then I think I might look into the EGR again, although the valve and solenoid checked out when I first started diagnosing. I just can't imagine what else would be giving the vacuum leak (kPA above 40, sometimes above 50 at idle).

 

OK, TTT.

I finally got my AC Delco EGR valve and replaced that last night. Drove the car today and it is better, but not yet cured. Still have light throttle bog/surge, and idle is bouncy at best. At (closed loop) idle, mV's are pegged above 800. Since it smells rich, is reading rich, and spit out a code 45 rich exhaust, I think the 02 sensor is ok. Also, as said above, MAP readings seem high, but I can't find any leaks. Is there anything else that could cause this?

So far, we have the following:
TPI 305/auto, 138k - only mods are K&N's and an Edelbrock cat-back (and did a TB coolant bypass when I put it back together last night)
2 years and 8,000 miles ago I replaced plugs, wires, cap, rotor, O2 sensor, and Cat converter.

In trying to diagnose the issue:
Replaced all 8 spark plugs
Checked for vacuum leaks, didn't find any
Checked EGR solenoid, tested good
Checked and replaced EGR valve (and cleaned passages)
Checked ohms on injectors, all checked ok
Checked vacuum line to FPR, no fuel
No apparent fuel in canister to TB line
Adjusted TPS to .57v at idle (was .62v)

I noticed today while looking at the datastream that the BLM's tend to trickle down from 128 to 88-91, then reset to 128 and back down again. One cycle takes about 6-10 seconds. I also noticed that the timing seems to go 20* before it jumps back to 128. Is it normal for timing to vary from 10-20* at idle?

I removed the connector for the MAP as suggested elsewhere to rule that out and it would put a fixed amount in the "formula". If it smoothed out, than it was the problem. Well, the car wouldn't even idle without it hooked up, is this normal?

The only thing left I can think of is to test that fuel pressure is holding. Idiot me put the car back together hoping the EGR would fix it, so I'll be ripped having to tear it apart again. I can double check the timing, but I don't think this would be caused by that.

Thanks for any opinions.

 

tell me if im wrong, but im pretty sure the base timing isnt supposed to change at all when idleing....

could be something with the ignition system/ecm ?

 

Hmm, let me clarify first - this is as read by my DataMaster scantool w/ the EST timing wire connected.

With that said, should this be a set value (fixed at xx* at idle) under computer control?

 

no with the est plugged in and the engine searching for an idle, the ecm most definetly will change the timing.

btw i actually had a very close to same problem on my tbi 305 which i never figured out (changed everything you did, and a little more and went through the same diagnostics as you). My blms stood at 108......... 02 mv's were averaging around 800 it seemed.....

Although mine was far from being tough to drive, it just idled rough and ran rich.

 

well honestly.. i think this is a no brainer.. the EGR.. haha.. this is pretty much the exact symptom they cause when they get crap clogged in them.. sometimes i can get lucky and just take it off and knock wutevers got it clogged out.. that makes customers happy when they dont have to buy 300 dollar electronic ones haha.. but when it gets stuck open it causes a vaccuum leak, which is why ur map would read high.. plus ur getting way to much recirculation of exhaust which also causes it to run like crap because ur not getting enough oxygen into your cylinders

 

I appreciate your input, but if you read the post (on 7/12) you would see I replaced the EGR and although its running better, it is still rougher than normal and MAPs are still high.

 

i also replaced mine on my l03 with a common issue. Mine made no difference at all, i also cleaned the hell outa the egr port with the manifold off even, to no avail.

I'll definetly be watching this with a close eye but honestly i went the same route you are with diagnosticsto no real avail, heres what i did to mine.

1. r&r egr valve
2. clean egr port on the manifold and pull the throttleody off cleaning the iac and pcv ports a lot (3 cans of carb cleaner to get it clean after 160k miles). This did smooth the idle a little but it was still rough and rich.
3. lots of injector cleaner, and the patterns looked perfect under a timing light
4. checked fuel pressure
5. 02 sensor
6. cut off cat
7. full tune up including fuel filter and pcv valve
8. checked vaccuum leaks wth propane to no avail.
9. blew out the return line
10. checked to see if the injectors were getting a good pulse with a noid light

yah some other stuff too but, i cant remember currently.

in your case running a multiport car where you can't see the injectors i would look in to having them professionally cleaned (we do this at work and it tends to make a huge difference).

On your car it could be as simple as a leeky injector pintle or plugged fuel pressure return line (would cause the system to run way more than needed pressure).

anyways considering what you've already done i'd opt to put a new fuel filter on if you haven't yet, and while its off i'd blow out the lines with compressed air. after that i'd have all the injectors cleaned at a local shop considering i doubt you have the equipment needed to do so properly

 

I just went thru the same problem..did all the "easy" things..finally checked fuel pressure..sure enough this was the problem..fuel pump! Major time consuming job but had to be done. I hope for your sake you have all day and then some to work on it.Have to drop the fuel tank..not an easy job..good luck!

 

Well, how long should the system hold pressure? W/ the pump on (engine off), it goes to about 40, when pump goes off, went to 38psi, and after about 30 mins was down to about 32. Tried it again and went to 43 w/ pump off, down to about 22 in 30 mins.

I'm pretty sure that's bad. Since I checked the vacuum line to the FPR and it didn't have fuel, I assume its at least one leaking injector?

Looks like I'll have to pull the plenum and runners again... Anyone have any 19lb injectors and/or AFPR they'd let go cheap? Next year I'm planning on swapping to an HSR so I'd prefer not to buy brand new stuff...

 

did you fix it? i have the same problem

here is what i did so far
1. deleted the egr
2. fixed a few vac leaks
3. removed the canister vac and pluged the vac source to eliminate as suspect
4. plugs, wires, cap, rotor, added msd6al and coil(all were old and arking)
5. swaped out the maf with a known good one
6. swaped out the distributer with a known good one (corrosion and exposed wires)

these were all issues that needed to to be taken care of but did not solve my problem, my blm's are at 108 and the idle is crap and very bad gas mileage as well as poor performance and horrible throttle responce.....but i stumbled on something today!
i measured the injectors current ramp and pulse width "at" the injectors and found that they were diff than what was on the data screen. i then checked them at the ecm (i think pins d15 for bank 1 and d16 for bank 2) with a multi channel scope and found bank 1 and 2 were firing erratically and at the same time...same pattern exactly!!! i then took out the ecm and ohmed out the bank one injector control wires (black with green) to the bank 2 injector control wires (black with pink) and found 25ohms!!! this means the banks are shorted together... basically i dont have batch fire! i have all fire lol both banks are fireing at the same time!

i dont know if any damage to the ecm is present yet but i will be swaping one from a buddies car after i repair the wiring

sorry for the book lol but this has been kick'n my *** for 3 weeks now hopefully this is of some help

to check this basically check for continuity between bank 1 and bank 2 injector wires black with the green and black with pink... they are 2 separate circuits and shoud not have contenuity! by the way thats with the ecm unhooked! to check the wiring, there should also be no continuity in the ecm as well

hopefully im right lol good luck

 

Well, just got done swapping the injectors. Come to find out the old ones weren't leaking (verified while attached to the rail but out of the manifold). I swapped them anyway since it was apart and they were Multecs. I also replaced the O2 sensor w/ a new AC to replace the Bosch, and replaced the original coil (138k!) w/ a new MSD unit.

I think it may run a wink better, but still not fixed. I did find a small vacuum leak, so it doesn't seem to be jumping rpm's as much at light cruise, but the idle is still consistently up/down. I have yet to be able to datalog because for some reason DataMaster sometimes gives my laptop the blue screen of death.

Does anyone else have any ideas? I think I have ruled out fuel but spark seems fine too. I haven't ohm'd the wires but I did pull them one at a time and all "changed" the idle...

I think tomorrow I'm going to call my trusted local mechanic, I'm out of ideas.

 

just for ***** and gigles try running it with the o2 disconcted...i know you put a new one in but just try it...oh if i cant spell its because im drunk sorry lol

 

Well, in open loop its still rough which would ignore the O2 so I can't see it being that. Maybe I'll have to double check the ECM like you said previously??? Seems like it would run alot rougher...

 

then took out the ecm and ohmed out the bank one injector control wires (black with green) to the bank 2 injector control wires (black with pink) and found 25ohms!!

Mike, I'm going to ask a dumb question.... when you checked the resistance of your injector banks ... you did remember to pull the fuses so that you wouldn't be reading across the positive connection ?
If you're using an O-scope ... I'm sure you would have thought of this already, but then, I've been known to have a brain-fart or two ... a day myself. (heck, this could be one of them, I might as well get started early today)

Tony

 

FWIW, here are the emissions tests before the last round (injectors, O2 sensor, and coil), but after the EGR replacement and the other stuff I tried:

HC 272 (limit 60)
CO 8.35 (limit .32)
NOx 377 (limit 700)

Here are the results from the test 2 years (and approx. 7k) ago, which was just after the tuneup mentioned in post #1.

HC 60
CO .04
NOx 515

Maybe that will help the smart people here!

 

well the nox went down, because its not burning the fuel as seen by the high co and the high hc, this engine definately is NOT in fuel control. are these figures at idle, high idle, or on an loaded emissions dyno? what are the values? ppm, grams per mile, percent?

when you finally get it straightened out do a top engine cleaning, the excessive co will cause carbon build up which will raise cylinder temps...then the nox will go up and possibly fail

just out of curiosity what is the injector pulse width? off the top of my head i think it should be like 1.7ish (dont quote me on that lol)

i asume you checked the timing...but just out of curiosity how is the condition of your balancer??? the reason im sayn that is i had a simalar problem with a 4.3 s10 blazer were the balancer spun a bit....in which the customer adjusted the timing themself to the bad balancer, i replaced the balancer and re-set the timing....just something else to look at

also slowly turn the motor over by hand (breaker bar) clock wise a bit then counterclockwise a bit back and forth all while observing the the distributor rotor to see if there is excessive slack in the timing chain... this can be a pain in the but to do sometimes lol

also i was going over all your posts in this thread and i didnt see anything about the pcv...i may have missed that tho, replace that along with the vac. hose and clean the passages. on mine i hooked a smoke tester up to it and didnt find the crack in the line that i could hear...cant figure that one lol.

at this point the oil may be fouled from the rich condition...change that if you smell fuel in the oil

uemf,
when i tested these it was with the all the injectors disconnected, the ecm unhooked and the battery and fuses unhooked, i was testing the ecm side not the power side...off the top of my head i think the power side for the injectors are the solid black wires and the ones with the tracers are the injector control circuit wires.... i ran new wires and they helped, the trans was rebuilt under the previous owner. who knows? there may be a few wires between the trans and engine lol, no wories tho, im replacing the complete harness...i have a lot of wires with broken insulation and alot of corosion along with the fact that im converting to map so its going to be basicaly plug and play lol

at this point i would totally go back to basics...check compression in all cylinders, cranking vac, running vac and needle operation (i.e. fluttering needle may indicate a sticking valve and so on), fuel psi...regulated...un regulated (vac source off)...fuel psi key on engine off, ignition system checks, vac checks.... i know you have done most of these but some times if you skip one simple step in diagnostics it'll bite you in the *** and you'll be kickin your self because the problem was right in front of your face lol been there and done that...lots of times

also what is your map readings again??? are they in in hg? kpa? volts? use a vac gauge to compare your readings here is a simple chart out of one of my books if the vac gauge is this...then the map should be this

vacuum @ sea level manifold absolute pressure sensor voltage
(in. hg) (kPa) volts
0 101.3 4.5
3 91.2 4.0
6 81.0 3.5
9 70.8 3.0
12 60.7 2.5
15 50.4 2.0
18 40.4 1.5
21 30.2 1.0
24 20.1 0.1

ill let you swollow some of that crap for now lol...i may have gotten carried away lol, i will look in some of my books and notes to see if i can find anything else usefull

 

I saw it mentioned, but didn't see if you had tried cleaning your coolant temp sensor connections. It seems something is keeping the engine in open loop, making it think it's cold, and adding fuel? Just guessing...

TA

 

No, I haven't. Temp readings are normal at the ECM, as compared to an Autometer electric gauge hooked to the DS head. Closed loop is also verified by scanner.

For sharts and grins, I put on a new AC cap and rotor after pulling the "Conrad Gold" piece put on in the tuneup 7k ago and looking at what appeared to be corrosion. Well, surprisingly, it seems almost back to normal now. Each step has gotten a little better so we'll see. Its been soo long since it was "right" I don't even remember. I'm not sure if the low alternator voltage made it corrode (that's when I noticed the running rough) or what. I kept concentrating on the fuel side since it was rich, K.I.S.S !!!

Tomorrow I'm going to retighten the exhaust and see if I can run it through emissions again and hopefully it passes!

 

Well, took it to work today, and I must have been on fumes because although better, there is still an issue. It runs much smoother, especially at cruise. But, it is still lazy, and at idle still bouncing around, just not as much. Also got the code 45 on the 35 mile trip to work. I'm and just plain out of ideas.

I think I'm really done now, off to the mechanic

 

just to let you know...fuel IS your problem...thats clear from the co readings. the hc readings genarally are for ignition problems and co is for fuel control problems, the high hc reading you have was due to a few things... to much fuel in the cylinders that are not being burnt and going through the exhaust (rich missfire) as raw fuel (which is what hc's are), also a poor ignition system will give you a higher reading

hc= unburned fuel
co= incomplete combustion

have you checked compression and valve timing (slack in the timing chain)?

ill try to find some info for you to read up on if your still intersted