Questions and Answers

BMW 325is Vibration Q. Hi Vince, I have a 1992 BMW 325is E36 rough idling problem. When the engine runs at idle speed (around 700 to 750 rpm), it's noisy and I can feel the vibration inside the car. But, when I rev my engine over 1,000 rpm, the engine runs smoothly and the noise level is much reduced. Here is the information about my car. 1992, BMW, 325i sedan 2.5 liter E36 Automatic transmission 50,000 miles Fuel injection ABS brakes P/S, A/C

The muffler has recently been changed. What are the possible reasons of the rough idling problem? Any fixes I can do? Can an engine tune up help? I just bought this car from my friend. He rarely drives (only 3,000 miles/year) and the car had been sitting in the garage for a few months before I purchased it.

Thanks a million,
Keith

A. The first thing I would do is examine the new muffler. Since it was changed recently and it sounds like this problem surfaced recently I would suspect that the new muffler is touching the metal on your car's frame or installation of it caused one of the exhaust pipes to touch the frame somewhere underneath.

If the exhaust pipes or muffler even appears to be close ie: within ¼" of the body or frame anywhere, then the system needs to be adjusted to improve the clearance.

Other causes of this type of vibration can be faulty or worn engine and transmission mounts but since you say the muffler was recently installed I would pursue that first.