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Q: RPM fluctuation, engine shuts off at the traffic light

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Hi. I have a few problems with my BMW. I had the worn fan belt replaced. I installed a new water pump along with the pulley. The issue is with the revving that seems to fluctuate a lot now. While I'm sitting in the car and not moving for a while, like at the red light, it would sometimes shut off. The steering is hard to turn as well. The engine doesn't seem to be overheated. Also, there are no leaks as far as I can see. Do you have any idea how I can fix this? Thanks.

You may have a belt tensioner not suppling enough tension on the belt. The power steering may also be low on fluid. The belt may be loose which will need to be adjusted tighter.

The idle problem may be due to the intake hose from the air filter to the throttle body. It may have a leak or is not sealed well, causing an air leak and the running issue. Have a certified mechanic diagnose your stalling symptoms and scan the computer for codes. Once this is done, a proper repair can be made.

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