I hope this is a simple question, well my problem started with a code 32 (EGR) also when it coded up 32 I had a low idle problem, so I cranked up the idle screw, so everything is fine idle smooth no rough idle problem. SO I went ahead and replace the bad EGR. The EGR was leaking diaphram had a leak. New EGR is in drop back the idle to 750rpm's, now no codes when driving on high speeds and long driving. But the problem now is its back to the problem I had before. When the ERG was going south the idle was alot better. An example of the rough idle is at stop you can fell the engine stumbling and you watch the rpms its jumping, sounds like the car will die out. These are what been changed allready.....New plugs, MSD wires, coil, cap and rotor. Checked all the vaucme hoses and replace whats bad allready.

 

Check the injectors (injector balance test). It could also be mechanical (worn cylinders, etc.). I take that since you've gone as far as testing the EGR, you've tested the fuel vapor system and checked for vacuum leaks? The injector balance test is easy to do, but you need an injector test kit.

Do you have a scan tool? Faulty injectors can cause the wrong air/fuel mixture and will show up as a rich or lean condition...most likely rich (for leaky injectors).

If all that is OK, try the compression test. Hopefully all is OK there.

 

Oh, when you cranked up the idle screw, did you disconnect the ECM? Reset the IAC using this procedure:

https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

 

Thanks for the info.

Injector balance test? You mean have it bench flow tested? If this is the case I will probally just buy new or used injectors. I had this idle problem before and the first thing I checked is vacume leaks. I borrowed a friends OTC and everything checked out good. BLM's are around 130 and TPS is not as high as it should even with a new one. IAC counts are on the lower side so its all good. I did a post and mentioned about the TPS adjustment and there is NO adjustment for the 92's 350 TPI. I broke the original TPS trying to enlarge the hole or something to get a higher voltage. And I did reset the ECM.

BTW where the orange wire power for the ECM.

 

The injector balance test checks the injector in the car. You disconnect the injector harness from all the injectors, hook up a fuel pressure gauge, and use this injector testor which hooks up to an injector (in place of the harness) and you fire off the injector at your control. You measure the pressure before and after, repeat for all injectors. If one or more injector is bad, it's variance will be more then 10kPa compared to the other injectors.

Or you could just replace them blindly, but this would tell you if the problem is due to a faulty injector.

Since your BLM is 130, I'm not sure if your injectors are faulty. A leaky injector would indicate a rich condition.

The other things to check for:
- faulty O2 sensor (doesn't necessarily trigger an ECM code). I normally just replace it instead of checking it.
- make sure your ignition system (caps, rotor, wires, plugs, etc.) are all good. If not, just run through a tune up.
- engine timing
- fuel cannister and valves operational
- check the AIR system
- compression test

 

any luck findin the problem yet?

 

sorry testing SIG

 

I bet you didn't even consider a bad or dirty IAC yet.

If the car otherwise runs fine, and will hold an idle with the idle screw cranked in, then it's about 99.9% sure you have a dead or dirty IAC.

Wanna verify real easy. When it's stumbling around, take the ducting off the TB and put your finger over the IAC hole (bottom between the blades). I bet it's not sucking, or if it is, barely. You can further verify by revving the engine while you're there. The IAC acts as a throttle follower / anti-stall device. So as you rev it, it will suck harder and when you snap shut it will continue to suck even harder for a second.

 

Well the stumbling is still there. After I replace the BAD EGR its don't code up now on long drives. I did remove the IAC a few times and cleaned it but the light stumbles are still there. I have a few friends that had the same motor in their Camaro's got the same problem as me (not getting a smooth idle). Well if I know for shure its the IAC thats causing this little stumble then i'll change it but its about $100 for it. Well thanks for checking up on me that very considerate of you and the others.

 

Clean the IAC housing. If your IAC was carboned up, so is the housing.

 

Yup did that allready

 

Like i said, it's very easy to test while it's running and the problem is happening. As simple as putting your finger over the IAC hole while it is stumbling. Hell, once you recognize the IAC whistle, you don't even need to do anything except listen from the front of the engine.

BTW, sometimes cleaning it isn't enough. They do go bad as well.

 

Ok I just removed the intake hose started it up, lots of air sucking from the IAC hole. If I cover it up the car will die out. So what's next?

 

Was the car doing it's stumble while you tested it?

Other than that, i'd put a scan tool on it and pray something jumped out at me.

 

See the weird thing is it will stumble more while in drive. And the last sentence did not make sense to me "pray something jumped out at me".

 

"pray something jumped out at me" means you connect to a scan tool and one reading obviously makes no sense, or is doing something weird, etc.

Especially if it's that intermittent, i just don't know how else you can capture it.

Which just gave me a revelation. You don't have headers do you? Or something else that might somehow be contacting something solid and perhaps giviong you false knock. I've heard of that happening, a header hitting the framerail whe the car is in gear because ofa slight shift in the motor mounts. And teh false knock retards timing, making the idle unstable.

Hey, it's weird, but in the end it could be something weird like that. BTW, the above problem is what i would call "jumping out on you if you had a scanner", they really do make life a lot easier.

 

A scan tool may be the quickest for something like this, as Ed suggested. There are many tests to perform for it. It might be worthwhile to pick up a service manual as well.

http://www.helminc.com/helm/welcome_...UWWVDDKJ6QCR73

There's a section for rough idle, with about 15 little tests to perform.

 

No headers just the stock manifolds. I did replace a bad knock sensor that was one of the many problems that I had ever since I got this car. So there is a new knock sensor in and that cured most of the idle problems. But I did us a OTC before and check all the sensors and seems to be in normal operation.

 

If you were to disconnect the Knock sensor would it just not send knocks to the ecm or would it not run at all? Is it necessary to have it plugged in, I know it would be bad to run it without it for a long time but say you just want to see if it is retarding timing how would you do this? I also have craig moates software and a comp that I hook up to my car every once and a while so what kinds of things would I be looking to Jump out at me?? so to speak

 

My IROC goes through periods where it runs roughtly. Not only at idle but revving it. The higher the revs the worse it is. It vibrates the whole car.
The only thing that will fix it is to disonnect the battery for 30 minutes. Works every time.