I have a 92’ 3.1L. MPFI Camaro. A friend and I have been spending a few months trying to fix a rough Idle. The only time it idles rough is at a stop, in Park and in drive. The car runs fine otherwise, no lack of power, etc. This is what we have done so far.

1. Found 2 vacuum leaks. Fixed
2. Check Engine light came on, car was running lean, so replaced the O2 Sensor. After I replaced this, there were no more codes in the computer.
3. Diode was starting to go bad in the alternator. Changed Alternator
4. Changed Spark Plugs, and wires (left cap and rotor)
5. Checked Engine Compression. All but Cylinder #1, because we couldn’t get the compression gauge to go in.
6. Last but not least, we checked timing, its dead on.

So, if anyone has some suggestions on what to check next, it would be very helpful, as we are running out of ideas.

Thanks,

 

you should change the cap and rotor. my friend has a 91 bird with a 3.1 and it was barely running, turns out it hadnt had a new cap and rotor in a looooong time and that solved the problem. also, when an O2 sensor reads rich or lean, it isn't always a broken sensor, it's throwing the code because something in the engine is making it run rich/lean and the sensor simply tells you that it is rich/lean, but since you havent gotten any codes since the new sensor i guess it was a bad sensor