Thread: Vibration ?????
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Old 03-01-2012, 10:16 AM   #3
Manolito

Name: Manolito
Title: Member
Status: Offline
Join Date: May 2006
Location: Sacramento
Rate My Car: 338 / 340
Your Ride: (2) '97 328s; '04 330; '04 325iT
The symptoms take me in several different directions as I read your post. The last line in your post takes us into a completely different direction.

Shaking on uphill grades suggests a load-related problem, which suggests a weak coil.

But you said it happened downhill as well and it was speed related. That suggests drivetrain components or wheel bearings.

Then you said it is happening at stoplights, meaning that either you have two separate unrelated problems, or the car is simply possessed by demons. The only thing that is at work in all three of these conditions is the mass airflow sensor, but if it were bad enough to make the car shake, you would be setting codes.

I would tackle the stoplight problem first so that its symptoms don't confound the speed related diagnosis. That problem is most likely an air or vacuum leak. Dismantle your air intake system and examine it for cracks. On an '04, the rubber hood on the throttle body is probably cracked by now (I have replaced both mine). Clean your throttle body while the hood is off. CAREFUL not to force the throttle plate. If you want to open it to spray cleaner through, turn on the key and have someone press on the gas.

If that is not the problem, get some starting ether and look for vacuum leaks.

Once the idle problem is resolved, we can start on the speed-related problem.
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