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#1 (permalink) Old 03-06-2005, 07:05 PM
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I've been having problems with my idle, especially when cold. Car is a 2000 540i, Dinan S2 (stage 5 software), around 100K miles. The check engine light is on and is giving codes for the intake system/airpump/check valve. Dealer is saying they're 99% sure it's due to a build up in the track between the airpump and the intake manifold. They're referring to a BMW service bulletin that's describing a similar problem. It's a 9+ hour service job, so before I have them do it, I want to get the boards input. Here's all the info:

-Air pump & check valve were replaced with new parts less than 2,000 miles ago, this did not fix the codes the OBD was showing. Idle problem was there before this and after the fix, although not as bad as it currently is.

-Idle hops from normal to 2500+ and then slowly comes down when first starting car, or when coasting to a stop and putting car into neutral. I really only notice it when shifting out of first or second into neutral and coasting to a stop or slowing down.

-When the idle goes up, the MPG gauge goes from normal reading (about center) all the way over to the far left (8MPG/far left) and then when the idle comes back to normal, goes over to the normal reading again (better than center to the left).

-The problem doesn't happen every time, and it happens more frequently when it's below freezing out. Doesn't matter how long the car's been driving (i.e. not just when the engine is cold).

-When at a standstill in neutral, the idle is not smooth. It's not rough like a misfire, but hops around a little (+/- 100 rpm). Sounds like the intake manifold leak I had on my old e31 (the v12's were notorious for it).

-Based on past experience with similar idle problems, I feel like it's an intake leak somewhere. I don't see where a "build-up" in the intake track is going to give these symptoms. I could understand a MAF malfunction, leaking gasket, cracked tubing, loose connection or something else, but "build-up" to me sounds kind of a last guess attempt to fix something.

Welcoming any input (especially from similar experiences)

TIA

-Rhansen162
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#2 (permalink) Old 03-06-2005, 08:18 PM
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Rhansen,
The dealership is most likely right on the money with their diagnosis of the clogged secondary air ports in the cylinder head in order to fix the check engine lamp problem. Im not so sure however if this has anything to do with the idle problems you are experiencing. Also this is much larger job than 9 hours. Unfortunately a lot of the m62 engines have had this problem. Normally this problem doesnt effect the idle however in your extreme climate I suppose anything is possible. Regardless, if you live in an area that has smog laws and annual checks you will have to get the problem rectified in order to register the car. While this is definitely not a cheap repair, at least BMW has come out with the cleaning kit now because before it was necessary to replace both cylinder heads. I would have the problem fixed and see if it helps the idle, but I wouldnt hold your breath. When they do the work they will be removing the manifold so they should be changing the gaskets. I would recommend they replace the rear PCV plate at the same time. Intake leaks and PCV probs have plagued the m62 and so this is more likely to help your idle problem than anything. When trying to diagnose a problem you must always start by rectifying any "known" issues, so I say fix the clogged heads and while they're in there do the intake/pcv stuff and then go from there.
Good luck,
DT

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