IAC issues, please help...

[Charlie C]

Working on an 06' twin turbo. Never had any issue until a week ago, my idle started acting weird. It would idle around 12-1300 RPS instead of the 900-1000 that it normally does. I pulled the IAC valve to clean it and it was already very clean. I was told that the IAC is just spring loaded and I should push it in and and let it come back out using my hands. I pushed it in and it stayed in. So I went to gently pull it out and it came apart. Damn... So I bought a new one, and installed it, now my idle is all over the place. Sometimes crazy high, like 2000 RPMs and sometime normal. I dont even have to push the throttle to take off from a stop. Only had the new IAC in for 45 minutes and 25 miles. Any ideas guys...??? Thanks.

 

[Viper Specialty]

Bad wire or terminal to the IAC. It is a stepper motor, not spring loaded. It should "pulse" one step at a time as it moves around. 4 wires, two step it in one direction, the other two opposite. You CANNOT apply constant voltage, it needs a PWM signal.

 

[Charlie C]

Ok, makes since. So, whats the issue with my car then. I pulled the new IAC and reinstalled the old one, plug it in and it will either Idle at 2000 RPMS or itll almost stall. I unplug the IAC and I have to give it a little throttle or the car will stall...

 

[bluesrt]

air leak possibly, do you have a hand held computer to hook it to?

 

[Viper Specialty]

Ok, makes since. So, whats the issue with my car then. I pulled the new IAC and reinstalled the old one, plug it in and it will either Idle at 2000 RPMS or itll almost stall. I unplug the IAC and I have to give it a little throttle or the car will stall...

What do you mean "what is the issue"? I just answered that above.

The IAC is an Idle Air Controller. If it has a bad wire or terminal, the IAC will stop in a random position and cease to do its job. Depending on where it stops, it will either idle high, idle too low and stall, etc. When it gets a signal again, it will start to move until it looses the connection again, and wherever it stops working is how the car will run until the next time it functions.

 

[Charlie C]

Ok, problem fixed. No bad wires or anything. Terminals were fine. I ended up disconnecting the battery, touching the Pos and Neg leads together to drain the power in the car, and clear the short term memory in the PCM. Then reconnected the battery. Turning the key to the on position but NOT starting the car yet. Just let the car sit for a minute, then started the car and let it idle for a minute. Not touching the throttle, brake or the clutch, once started, just let it idle. Then took her for a test drive and it was all good. Perfecr idle, and no surging or stalling or crazy high RPMs at a stop. Thanks for you guy's help and thanks to Will from RSI. As usual, he and his crew took care of me.