1998 BMW 740 ENGINE VIBRATION

  • Tiny
  • jt1966
  • 1998 BMW 740

Engine Performance problem
1998 BMW 740 V8 Two Wheel Drive Automatic 285000 miles

I have a 1998 BMW 740iL with hijgh mileage. The idle is bad causing car to vibrate an it has a rich exhaust smell. Compression test reveals that all cylinders but one( number five is reading 150. But number 5 is reading 75. If this helps, the service engine light stays on constantly in yeloow and the asc/dsc light and abs light is on all the time.

Already replaced spark plugs.

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Wednesday, June 2nd, 2010 AT 6:56 AM

3 Replies

  • Tiny
  • mhpautos
  • Expert
  • 30,561 posts

Hi there,

The low compression is a big concern, I would first get a wet comp test done as this swill help determine weather it is rings or calves at fault, also a scan to read the unresolved fault codes.

Mark (mhpautos)

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Wednesday, June 2nd, 2010 AT 7:09 AM
  • Tiny
  • jt1966
  • Member

Thanks for the quick response and help. Should I be considering an engine rebuild. Or for that matter an engine?

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Wednesday, June 2nd, 2010 AT 8:18 AM
  • Tiny
  • mhpautos
  • Expert
  • 30,561 posts

Hi there, I feel that at the mileage you have a top end o/haul will be fraught with danger as this will load up the lower end, I would be considering a full o/haul or a re-co long engine, but a wet comp test will tell us a lot and I would also get the valve clearance checked as a tight valve can cause this as well, best to know exactly what we are looking at first.

Mark

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Wednesday, June 2nd, 2010 AT 8:29 AM

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