2000 Impala 3.4L idle problem

[JohnT396]

This car has 250,000 miles and has been pretty solid. Recently, I have been having an idle issue in that unless I keep my foot on the pedal, it will stall. I cleaned the throttle body and all the ancillary add-ons yesterday and did not resolve the problem. I was left with simple adjusting the idle screw to raise the RPMs. Easy fix, but I thought the engine controls/computer would make any adjustments needed. So I feel that what ever the problem is, it has not gone away. BTW, there are no codes and no CEL so no clues there. Any suggestions?

[maxwedge]

Get that base idle screw back where it was that is factory preset, the tps will have skewed inputs as a result, remove the iac and clean it and the passages, make sure the egr full seats also.

[Tech II]

By increasing idle with idle screw, I bet that tranny jumps in gear or has a harsh feel when put into drive....

Hard to believe no codes are set......I have a tool that attaches to the IAC to make it increase and decrease idle, to check the IAC....a bi-directional scan tool is better, since you can increase/decrease idle via the IAC through the PCM....

It's possible the IAC is bad, or the circuit to it is bad, or you have a PCM problem....

These days, it's almost impossible to diagnose problems without a scan tool, even if it's not bi-directional....you can see the rpms and also see the IAC counts, to see if the PCM is commanding the IAC open.....

[Bdd8591]

Have seen this on a couple. Try starting the car and play with the connection at the MAP sensor thats what it was on mine. Worth a try

[JohnT396]

I just wanted to close this thread and thank you for your suggestions. The ultimate fix was replacing the IAC. Everything is set back to original settings and all is well!