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740 vibration / misfiring (?) issue

Mr. V

Active member
Joined
Jul 5, 2004
Location
Portland, Oregon metro
'86 740 Turbo, manual transmission: well maintained / rebuilt engine.

For many years I've had a problem that I cannot solve.

At a bit over 2000 Rpm, more especially when not fully warmed up, it will transmit what seems like a vibration through the wheel; lasts almost to 3000 RPM then clears.

Suspecting a driveline issue I took it to two pros, but both lack the equipment to check and balance it, I believe due to the rubber inferface between the shaft and the transmission: anybody know of a driveline shop in the Portland area that can in fact check it?

It may not be the driveline; it isn't tires and wheels because I upgraded without any change.

Suggestions?
 
Is the vibration in that rpm range in every gear and in neutral? If so its not likely drivetrain. Have you checked engine and trans mounts?
 
Seems to be while under load, i.e. while accelerating normally, and fades when put into neutral.

Assuming it is not tires or driveline and is likely fuel or spark related.

What to check and how to check it, as the car is too old to give any codes?
 
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