TPS, Running Rich, erratic idle

Hi all,

My son has a 1989 Firebird, V6, 2.8L 5spd. The car had set for some time when he bought it and we have been going through it all. To date, we have done the following:

Replaced the timing chain, water pump, radiator, thermostat, expansion bottle, IAC, coolant temperature switch, TPS, plugs, wires, rotor cap and bug, and set the timing to 10 btdc.

The car starts fine, but idles erratically until it reaches normal operating temperature. The exhaust is rich, and we are receiving a code 22, which is the TPS. I repulled the TPS and replaced it again with a new one. Unplugged the battery to reset the codes, and then restarted again. After a few seconds, the check engine light comes on again and it's a code 22.

I don't know if all of this is caused by a vacuum leak, the EGR valve or if the TPS is shorting out or faulty or if it's something else.

If anyone has any suggestions, I'd be very grateful.

Thanks,

Pat Rogers

I have readjusted the TPS and the code 22 has gone away. I had to move it all the way forward and adjust the idle screw in order to receive around 4.5 volts between the black and blue wires.

It is still running rich and I'm not sure what else to try on that. What are the chances that the EGR valve needs replacing? The charcoal canister smells like gas fumes, but everything is hooked up fine. There is also a small crack at the top of the muffler, I don't know if that would allow such a rich smell from the exhaust.

At this point, I am at a guessing game as I don't want to just start throwing parts at the car. When I press under the egr valve on the diaphgragm, it moves ok, but not real freely. I don't know if that would cause this problem. When cold, it still idles roughly, but after it's warm, it does idle fine, around 900 rpm.

I have replaced the coolant temperature switch as well. Also the PCV valve.

Please, any other suggestions would be so appreciated. My son's 16th birthday is next thursday, 10/20, and I'd so love to have this car working well.

Thanks in advance for any suggestions.

Sincerely,

Pat Rogers

Sounds like either inaccurate O2 sensors or a inaccurate MAF. I would consider logging or scan the car while its running and look at the sensor feed for the O2's and MAF. Good luck Pat

Sounds like either inaccurate O2 sensors or a inaccurate MAF. I would consider logging or scan the car while its running and look at the sensor feed for the O2's and MAF. Good luck Pat


Thanks so much for your reply! I really appreciate it. I didn't consider the O2 sensors, and that is probably a great place to start. I will have to see where I can rent a scanner to check the stats on the MAF and the O2 sensors. Thanks so much again for the advice. I'll repost when and if I find anything new!

Thanks,

Pat Rogers