I have an 87 IROC witht he 350 TPI. Car Idles fine at startup. But when it get warm and while driving, idles like crap. Constantly increases and decreased idle speed while in gear. Levels out (mostly) when in park or neutral. It has even started dying periodically when you come to a stop light. If you put it in neutral and rev the engine; when you let off it dies. The car has underdrive pullies on it and voltage drops as idle when in gear. I don't think that this is the problem though. I am thinking it is the Throttle Position Sensor but don't know. Any suggestions would be helpful and appreciated.

 

From the sounds of things, I would look towards your O2 sensor. I say this becasue your ecm will ignore your O2 values until your engine reaches operating temperature. When is the last time you changed that badboy? They say you should get a new one every 30 K or so, but there are ways to ruin one before you get that much milage out of it.

Have you scanned your ecm or checked it for codes? That would be a good place to start if you don't want to just go and buy a new sensor w/o diagnosing anything first.

Good luck!

 

I did run the codes and got a code 32. That is EGR related and should not be related to my idle problem or is it?

 

A bad egr system can give you a bad idle. However, Egr systems have been known to through their ses code while they're still in fine working order. My car actually did this. I found a code 32 on it one day and then reset the computer to see if it would come back and I haven't seen it since. You actually might want to do this same thing. Disconnect your battery for a minute or so and then hook it back up, go for a long drive, and see if the ses code is there again. If it is, than I would say your egr is part of, but maybe not all of, the problem.

Chances are it won't come back, and in that case I would tend to concentrate on your O2 sensor for these reasons:

-Your problem doesn't happen when your engine is cold (or in open loop, which is when the computer ignores the O2 readings)

-The O2 sensor is easier to get at and way cheaper (~1/5 the price of the egr valve) to replace than the components of the EGR system

-If you can't remember the last time your O2 sensor has been replaced it needs to be changed regardless of your egr's condition

I am interested inthe outcome, post what you find.

 

Just where is the O2 sensor located and any suggestion on P/N,
price and source. Thanks

 

Driver side exhaust maninfold, it has a single wire going into it. I would suggest going under the car to change it. Be carefull not to contaminate the actual metering end of the new one before you put it in, gettting certain things like coolant on it can ruin it. Some recomend going to GM for a part this crucial to performance and mileage. Me, I got my last one from autozone, a standard car parts store in the area. Either way call ahead and give them the specifics on your car and engine and they will let you know the availability and the $.

 

I had almost the exact same issues that you are having now. I ended up having a bad ECU and a bad MAF sensor. My TPS sensor was also bad.

It sucked. I went through everything myself before finally putting the car into the shop. Everything I replaced helped just a little bit. But it wasn't until my ECU was replaced that the problem cleared up. There are a whole host of things that can be the cause of your issues.