1985 BMW 735 timing chain

1985 BMW 735
325,000 MILES • 6 CYL • 2WD • AUTOMATIC
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85BIMMER735
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  • 3 POSTS
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
Mar 12, 2010 at 6:28 PM
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MATHIASO
  • ✓ASE Certified Mechanic
  • 1,209 POSTS
  • ASE Certified Mechanic
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.
Mar 13, 2010 at 8:45 PM
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