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Old 10-08-2012, 07:57 AM
thompsonmd thompsonmd is offline
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Location: Iowa
 
Join Date: Jul 2010
Posts: 45
Mein Auto: 2006 X3, 2002 330i
Rough Start, Then Fine - lean engine codes

Guys, thanks in advance. I always come back when something goes wrong and somebody points me in the right direction right away.

2006 BMW X3 3.0, 85k, fresh off warranty (of course).

Upon starting the engine runs rough for a few seconds, then it is fine. By rough, I mean the RPM fluctuates. As soon as the gas is applied or a few seconds pass, it operates completely fine. Acceleration, MPG, oil consumption, all fine.

It only does this if it has been sitting for a few hours. Always does this overnight, whether parked in the heat or cold, or humid or dry.

Occasionally, anywhere from a few hours to a month, it will throw the lean codes for both banks, P0171 and P0174. Has done this for about 4 months. Never any other codes.

I have replaced the filthy air filter, cleaned the MAF, and even replaced the plugs. I have superficially inspected the air intake as far as I can without removing anything except the air box, or getting under the engine. The rubber all looks fresh and I can't see any cracks, or hear any whistles or leaks when it is running.

I stopped by an indy shop for brakes and told him the issues. He suggested that perhaps a fuel injector slowly leaks when the car is off, building up fuel in the cylinder. Then it is cleared out after a few revolutions.

Any thoughts?
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Past ownership: 1987 325is, 1988 325i, 1995 325is, 1996 325i Convertible, 1994 325is black coupe (which I miss).

Current ownership: 2002 330i Sedan with some cool DINAN upgrades, 2006 X3 3.0i

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