First symptoms: High idle after getting off freeway (2000 rpm) sometimes, maybe 1/10 times.
Actions: clean out IACV, reset idle and timing.
Results: High idle every time I get off the freeway.
Actions: clean IACV again, used about 2 cans of carb cleaner
Results: no idle problems for a few months.

Current Symptoms: High idle after getting off the freeway. It's happeneing more and more often. If I turn off the engine and restart it, the idle drops to the correct RPM.

Suggestions?
Should I just clean the damn thing again and hope it works for a while?
Is there a way to test the functionallity of the IACV?
Give up on cleaning it and replace the IACV with a new one (they're not cheap, $200+)?

 

My hatch did that, i just adjust the little allen head screw on the iacv. Dont know if that was actually the problem but it fixed it

 

very unlikely that the IACV is bad. if there was a problem with the unit you would mostly likely get a CEL anyways.

double check for any vacuum leaks. then you should try setting the base idle.

get the car up to temp, then unplug the IACV. the car should idle around 400rpm. if the car dies or is idling higher, adjust the idle screw until the car idles at 400 with the IACV unplugged. once set, replug the IACV and clear your CEL.

 

Thanks for the responses.
I don't know anything about any allen screws on the IACV...
I am very sure there are no vacuum leaks, or symptoms of a vacuum leak.
I did set the base idle to ~450 with a digital tach.

Another thing to note, this only happens when I start driving while the car is cold. If I let it warm up completely before driving, or start the car when it's already warm, I have no idle issues. If I turn off the car for 1 second and turn it back on, the idle drops from ~2000 to ~700.

It's like the IACV is stuck open and won't close until I kill the power.

Is there any way to bench test an IACV?

 

there isnt an allen screw, there is just a flat head screw on the throttle body.

does the car have an FITV? this would effect idle during cold start-up

 

Help us to help you.

What make and model is it? Any check engine codes?

 

iacv could be bad and no cel will come up... very rare a iacv goes completely dead, which would then throw a cel... my dc lsr had a bad iacv, it wouldnt hold a steady idle, never got a cel.

 

since you said you cleaned it, and was fine for a few months, i would look into iacv

 

yea, i'd definitely try another valve. you sure the system is bled thoroughly?

 

i was thinking same thing... but he said it was fine for a few months, he wouldve noticed immediately, if it wasnt bled properly

 

Yeah, it's probably just dirty again. The car is in my sig. No air in the coolant lines.

No CEL's, just a high idle after warmup. I swear the IACV is getting stuck. I suppose that's the point of the Clean out your IACV FAQ.

I'll just clean it again and buy a new one if it still annoys me. It's hard to justify 200$ on something that has such a simple workaround (OFF-ON). I was actualy looking for a way to bench test the IACV and see if it's getting stuck opening or closing.

 

Are you going to answer my question?

EDIT Yes, just saw his last post, sorry for the repeated question.

 

I think its the car in his sig

If it is, is the car tuned?

 

Yea i saw that, just wanted to make sure. Also just saw his post before my last one.

To the OP, sounds like the iacv. Have you tried swapping with someone who has a known good working one? Only a high idle after warm up? how high does it idle when warming up?

 

well the only way really that it's going to idle high is with more air past the throttle plate.
so it's either the iacv, or a vac leak.
try another known working valve. if that doesn't fix it, check for a vac leak using a can of quick start. wouldn't be a bad idea to service the throttle body as well

 

Finally figured it out after 6+ months of troubleshooting. I bought a new IACV, no changes. All the sudden my car started running like crap while cruising and then later threw a p030# code for cylinder 3 misfire. Changed the plugs and the problem went away.
Thanks for all the help and replies. Oh and the car is stock right now, 2000 GSR.