I just installed a new Idle Air Control valve, and though it turned off the SES light, now the car won't idle correctly.

When I start it up from cold it launches to 2 grand and holds there until steadily the car warms up, it then backs down to about 1400, but once the car is warm and I drive it down the street the idle will start bouncing from 1400 back to 2000 RPM, and back again, and back again...

Any ideas? And I know I didn't touch any vacuum lines since it's a relatively easy part to switch out, so I don't see how a vacuum line could have popped off or changed in any way. I reset the ECU by unplugging the battery and hitting the brakes a few times, but I'm out of ideas.

I know, I know, there's been a ton of IAC threads made, but I can't seem to find anyone that's had a bouncy idle right after install like mine.

 

i had the same prob after i changed mine but mine went away on its own i dont know how long this has been happening for u but idk what to tell ya

 

How long before it went away? I'm thinking I didn't tight my UICP tight enough and maybe that's causing a leak? I just drove it around the block once and came back once I noticed it being retarded.

 

disconnect the battery for a little and see if that helps.

 

Omfg, so frustrating, the idle's now set at 1800 rpm, it won't come down from that, and the SES light is back on again. Seriously, is my brand new part already broken?

 

easy, most likely idle screw was adjusted improperly without first parking it in evoscan. also target idle w/ AC is way off, thats why IAC is fighting what you set(and causing bouncing idle)

now that you put in a new and working IAC, set the idle via ecuflash, then set SAS mode to park the IAC then adjust idle screw to where you wanted it. dont forget bring up the car to temp before parking the IAC.

 

The only thing I can say is do a boost leak test and then you can see if you have a vacuum/pressure leak. Don't forget the soapy water. I have had bad Iac o-ring's before.

Disconnect battery, Start car,idle for 10 minutes. Car will re-learn idle to a stop after a couple drives.

Good Luck

 

Hmm, now I just need a tactrix cable and evoscan. What do you mean by "parking" the IAC? Would an ECU reset have changed anything?

 

It sounds to me that the thing is just not working. Are you sure the electrical connection does not have any bent pins and is fully plugged in?

 

I'm going to take it back out and see if it's stuck or something, something isn't right.

 

Parking the IAC (stepper motor) is under the actuator options on the right in Evoscan.

 

Listen to this guy

 

Just an update:

So I finally figured it out. After installing the IAC the idle screw was raised way high to compensate for the bad IAC originally. So the ECU wanted ~900 rpm but the car was set at 1800 to compensate for how screwed up the broken IAC was. After letting the car idle and warm up I reset the ECU so the SES light went off, restarted the car, and proceeded to adjust the idle screw back to 900. At first attempt it didn't work, I don't think I adjusted the idle screw close enough to what the ECu wanted, so I went for a run around the block, came back, let the car idle for a minute and shut it down. I reset the ECU by disconnecting the battery again, restarted, and once again the SES code was gone, so I adjusted the idle screw a little bit more until the car was idling again at a nice ~900 rpm. Haven't had an issue yet.

Like an idiot, I should have just played with the idle screw from the beginning until it was idling at ~900. Just for anyone that reads this in the future, the idle screw is on top of the throttle body, in a little hole. You'll need a shorty phillips/flathead screwdriver to reach it. Clockwise lowers the idle, counter-clockwise raises it.

Thanks to everyone else that helped and posted.

 

It's called Idle Surge.
If you didn't disable (park) the ISC in the neutral position, the BISS, most likely, still isn't set right.

 

bumping:


thinking it's the IACV and BISS need to be reconfigured, any thoughts?