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BMW Idle Speed Varies Occasionally


My son owns a 2000 BMW 328i… sporadically, and without warning, the motor will speed up at idle, going from 600 rpm to 1200 rpm, then down to 700 rpm, then back to 600 rpm. This happens intermittently, when the motor is warmed up… any ideas?

Do you have a record of some warranty work that would have involved the replacement of a large vacuum hose under the valve cover? this hose cracks and causes a vacuum leak, most if not all were replaced under a campaign. I was dispatched a 2000 328i with customer complaint similar to yours (this was before the campaign started)An extensive test drive did not reveal any concern until my final stop in the parking lot, then the idle got very erratic. I finaly found the leak simply buy the use of a visual inspection, a bit latter the campaign came.

Thanks for the reply… No records of warranty work… When he bought the car (used), the independent mechanic replaced the radiator overflow tank and suspension bushings… Question: since the hose is noted in a “campaign”, does that mean that it would be replaced by the dealer for free? I’ll forward your response to my son, so he can inspect it himself. Thanks again.

Yes it does,this was a full on campaign by BMW. I will see if I can find a number.

EDIT: This is listed as a voluntary effort by BMW and techs are instructed to replace this hose the next time the car is in the shop. These parameters make it more likely or possible your car was missed. Service Bulliten 11-09-01 Campaign 02E-A01. When this hose leaks (you cant see the hose it is under the first layer of covers above the cylinder head) misfires,rough idle,check engine light is possible. Replacement takes a trained man about 10 min, one end of the hose has a tricky to disconnect coupling.