High Idle After Warm Up

[triton6346]

So my car has been driving well after a series of electrical issues involving the throttle body, throttle position sensor, MAF and clutch position switch were implicated and subsequently replaced. I had a host of problems related to the EPC and EPS lights coming on, super-limp mode happening and so on. Major PITA! I worked on a few harness connectors, replaced some parts and the problems have been absent since July or there about. To be 100% honest, I never found a smoking gun in all my attempts at hunting and diagnosing, but I just worked through the codes that were popping up and implicating these parts. The behavior just went away which is a little un-nerving, since I’m not exactly sure why. But it’s been solid for a while now.

As of this week, I now have an issue with a high idle that seems to happen after the car does it’s warm up process and is driven for a bit. The car starts and idles at about 1000 rpm for a minute or two…depending on temperature I think, and then it settles down to around 900 or so. I drive the car for a distance…doesn’t seem to matter how far, and then the idle goes to somewhere between 1000- 1200 when I come to a stop and take it out of gear. Car drives fine otherwise.

This just started happening yesterday, so I haven’t really had a chance to do much other than search the forum for similar symptoms. Plus, it’s cold out now and I tend to pick my days for wrenching when the suns out. There is no CEL, and I plan to scan it with VCDS in the next day or so to see if there are any DTC’s present. It kind of feels like a vacuum leak type of problem, but I have no real basis for that yet. I’ve been reading about intake flapper linkage system, with the idea that it’s maybe sticking open/closed or whatever it does. I also found a few posts about the airbox valve. I dunno yet…trying to pick a place to start the process. Where would you guys start looking?

[eurojunkjon]

Mine is doing that now but I do have a vacuum leak coming from the throttle body gasket.

[triton6346]

Eurojunkjon. That's the thin gauge metal "gasket", right? Hmmm...I suppose I should make sure all the connections around the TB and MAF are good and tight since those were replaced. Prolly a good place to start.

[VinnysS4]

I would definitely start with a vcds scan and a good look at the fuel trims once it is warmed up. If you have a abnormally High fuel trim, that would indicate a vacuum leak. ( A+ fuel trim means it's adding that percentage of fuel and a negative fuel trim means it's pulling that much fuel out to reach stoichiometry)
my guess is you're going to have a high positive fuel trim. If this is the case, you can find the vacuum leak pretty easily with a can of propane and an unlit torch, you could use starter fluid or brake clean, or you could do a smoke test. I know it probably won't help, but also run a throttle body alignment just to make sure it is aligned properly. Especially with the electrical problems you have been having.
From my experience, and abnormally high idle is usually indicative of a vacuum leak of some sort. I had a breather hose come loose off of one of my valve covers and my motor would idle exceptionally High after that, and RPMs would kind of go up and down at idle while the ecu was trying to correct the problem.

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[megarex]

I had this happen on my last b7, PVC valve replacement fixed it. I also replaced the ^^ breather hose. Second time around my fuel trims were fine and it ended up being an airflow issue from a failing throttle body motor, fixed after replacing it.