1998 BMW 740 engine vibration

1998 BMW 740

285,000 MILES • V8 • 2WD • AUTOMATIC

JT1966

MEMBER
2 POSTS

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.

Jun 1, 2010 at 11:56 PM

MHPAUTOS

✓Experienced Mechanic
31,937 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)

Jun 2, 2010 at 12:09 AM

JT1966

MEMBER
2 POSTS

[quote:2dcec1dd25="mhpautos"]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)[/quote:2dcec1dd25]Thanks for the quick response and help. Should I be considering an engine rebuild. or for that matter an engine?

Jun 2, 2010 at 1:18 AM

MHPAUTOS

✓Experienced Mechanic
31,937 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

Jun 2, 2010 at 1:29 AM

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