1985 BMW 735



March, 12, 2010 AT 6:28 PM

Engine Mechanical problem
1985 BMW 735 6 cyl Two Wheel Drive Automatic 325000 miles

My car runs good for about 15 minutes but then backfires and dies I just replaced both fuel pumps and all the ignition components my brother inlaw said it sounds like a timing chain but I'm not possitive what do you think any imput would be great and if you know how to check the timing that would be awesome also

1 Answer



March, 13, 2010 AT 8:45 PM

Hello 85bimmer735

A stretched timing chain can affect both valve and ignition timing. If the wear is severe and the chain jumps timing, the engine may run rough and/or possibly backfire but why 15 minutes?
I'll suspect a bad catalytic converter.
Raise the car, using a soft hammer tape on it, listen for any rattling noise.
Or check intake vacuum at idle. If intake vacuum reads low and continues to drop, inspect the exhaust system.

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