Hi, my 89 2.8 auto firebird is idleing lower than usual, about 500 - 600 RPMs. It uses to do between 700 - 800 or so I think. It has only stalled twice within 1 week but hasn't done that in a while, although it does a little reverse surging or something like a chug at idle one and makes me think it will stall somethimes. It is fine as soon as I give it some gas and part throttle to WOT doesnt seem to be affected. It seems to have a problem in idle only. Also I seem to have lost a little city MPG I think but highway seems to be ok but I haven't really check either one. Maybe thats in my head. I have upgraded my ignition electral parts. I have a brand new accel coil, accel ignition module, accel cap and rotor, MSD 6A box, MSD wires, the plugs are fairly new, only 20,000 miles on them and they are 100,000 mile bosch 4 prong ones. I looked at them and they look ok. I have also replaced the pick up coil last year. I also had the timing done a couple months ago. So I think the electral ignition area is ok and well covered. I also have a flowmaster muffler. PCV valve has been changed recently and I have a fairly new K&N filter. I was thinking since my Cat converter is the orginal factory one and has never been replaced could this cause that if it were plugged? Might explain why its only having a problem at idle and not when there might be more exhaust pressure in higher throttle? I thought fuel filter and I might change that anyways but I would think it would have more of a problem at higher throttle where it would need more fuel and would be starved for it. What do you guys think? Am I on the right track? Any other ideas on what it might be or suggestions. The car has had a pretty good tune up and I am aware of Tom P's major tune up. Any ideas welcome! Thanks... Erik

 

You know my pet peeve... EGR.
If IAC, and 02, and TPS, MAP/MAF are fine...

Sounds like it could be sticking sometimes.
Remove and clean 'n replace.

 

Pull your IAC, clean the pintle and spring with a toothbrush and carb cleaner. Clean the air passages in the throttle body. Clean the throttle bore itself around and behind the butterfly, clean the butterfly itself front and back, reassemble and reset the computer.

Sounds like its gummed up to me. I have to clean mine every 6 mo's to a year.

 

Just replaced my O2 sensor, I will take apart my IAC and throttle body and clean them. I had checked my TPS sensor not too long ago with a scan tool and it was reading the correct voltage. I also have checked my EGR but I will again. They way I did it was by putting a screw driver on the underneath side and reving the motor and it did raise and lower. I will check again though. I no longer have the scan tool so is there anyother way to check my TPS? Could it be cat convert in combination with these other things?