Idle hunting issue

[Durandal]

I have been having an issue pop up recently now and then but not consistently. Sometimes my idle will surge from 1000 to 2000 as if I have a disconnected MAP sensor. Other times it will idle high at around 1200-1300. When I step on the clutch the idle drops down to 1000 for a second but then back to 1200-1300.Any other time it idles normall at around 1k.

I've checked for boost leaks and just cleaned my IAC valve last summer so I don't think those are the problem. Is the first butterfly closest to the front of the car in the throttle body suppose to be closed all the way? It seems to be open a little bit in the closed position.

*Should mention that I am getting no codes

[pwpanas]

Originally Posted by Durandal

I have been having an issue pop up recently now and then but not consistently. Sometimes my idle will surge from 1000 to 2000 as if I have a disconnected MAP sensor. Other times it will idle high at around 1200-1300. When I step on the clutch the idle drops down to 1000 for a second but then back to 1200-1300.Any other time it idles normall at around 1k.

I've checked for boost leaks and just cleaned my IAC valve last summer so I don't think those are the problem. Is the first butterfly closest to the front of the car in the throttle body suppose to be closed all the way? It seems to be open a little bit in the closed position.

*Should mention that I am getting no codes

Although you checked for this last summer, a boost leak could happen at any time (eg. a cracked hose). I'd advise you to check this again. Another possibility is a dirty Idle-Air Control valve.

I doubt your secondary throttle (the one for the oem traction control system) is related. This butterfly should be fully open most of the time, except when your traction control system is triggered.

[Durandal]

Yah I've been leaning towards a small boost leak. I had a boost leak awhile ago where one of the accordion style rubber pipes above the turbos was loose but I fixed that.

I had my exhaust from the turbo manifold back removed last year to look at removing the stock cats but didn't do anything with it and just put it back on. I don't think an exhaust leak there would be causing this though. I guess I'll rig up one of those homemade boost leak testers and check my IAC just to be sure.

The thing is if I keep my foot steady on the pedal under boost, my boost gauge stays constant and doesn't drop off.

*edit: Did another visual inspection today and found a couple hoses with small cracks on the ends of them at the EGCV VSV and a some above the turbos. Going to look at replacing them although they don't seem to be leaking.

I give the car a cold start and it idles at around 900 which is good, but after it warms up the idle goes up to 1100-1200. I take it for a drive to test my boost pressures and am getting around 8 psi from turbo1 until turbo2 kicks in at 4000 RPM and my boost pressure goes up to 14 psi.

I did add some fuel injection cleaner last time I got gas but that wouldn't increase my idle 200 RPM would it?

[wstanek]

possibly if ur injectors were clogging and that cleaned them mabey ur getting higher rpm cuz o more fuel! =D

[pwpanas]

Originally Posted by Durandal

Yah I've been leaning towards a small boost leak. I had a boost leak awhile ago where one of the accordion style rubber pipes above the turbos was loose but I fixed that.

I had my exhaust from the turbo manifold back removed last year to look at removing the stock cats but didn't do anything with it and just put it back on. I don't think an exhaust leak there would be causing this though. I guess I'll rig up one of those homemade boost leak testers and check my IAC just to be sure.

The thing is if I keep my foot steady on the pedal under boost, my boost gauge stays constant and doesn't drop off.

*edit: Did another visual inspection today and found a couple hoses with small cracks on the ends of them at the EGCV VSV and a some above the turbos. Going to look at replacing them although they don't seem to be leaking.

I give the car a cold start and it idles at around 900 which is good, but after it warms up the idle goes up to 1100-1200. I take it for a drive to test my boost pressures and am getting around 8 psi from turbo1 until turbo2 kicks in at 4000 RPM and my boost pressure goes up to 14 psi.

I did add some fuel injection cleaner last time I got gas but that wouldn't increase my idle 200 RPM would it?

Agreed fuel injector cleaner wouldn't cause it. However, it wouldn't take more than a very small-sized hole to create enough of a boost leak to raise your idle. However, that small sized hole wouldn't necessarily be big enough to cause a noticeable a drop in boost pressure on the high end (total air volume is many times more under load and higher rpm while boosting).

[Durandal]

What would cause my cold starts to not idle high at all? Right now my cold starts the same as hot starts and idle at 900 instead of over 1k like it should. The IAC is used after it warms up right? Or do I have that backwards.

[pwpanas]

Originally Posted by Durandal

What would cause my cold starts to not idle high at all? Right now my cold starts the same as hot starts and idle at 900 instead of over 1k like it should. The IAC is used after it warms up right? Or do I have that backwards.

The IAC is open during starting and cold-engine operation. Throttle plate is sealed shut unless you press the accelerator. There should be no vacuum leaks other than the IAC. In other words, the IAC is the only path for air into the engine, so it must be open for initial idle. While cold, the idle rpm is higher (so the IAC is actually open its widest during cold idle); a/f is also richer during cold/cool engine conditions. The IAC closes a bit after the engine warmed up to reduce rpm.