Re: 1997 Buick Ultra Transmission

Bad plug wires.

Changed the plugs and wires yesterday. No difference in idle vibration. Looked over the plugs thinking that maybe it was a bad ignition pack and all the plugs look the same (brownish residue). I'm back to square one so I'm still looking for advice.

Wires and plugs were a good thing to try first. Now it gets harder. It sounds like there is more than one, perhaps several, non-related problems. The vib at speed could be wheel balance, etc. The hum & vib @ 80 could be wheel balance, wheel bearing, cvj, etc. The rough idle could be due to a lot of things: injector(s), vac leak, warped/bad intake manifold leaking antifreeze into the engine (3800), dirty throttle plate, dirty bad maf/mat/iac, and a bunch of other things. Probably NOT ign.module, coils, or trans. Check those out first and let us know what you find. Paul.

Wires and plugs were a good thing to try first. Now it gets harder. It sounds like there is more than one, perhaps several, non-related problems. The vib at speed could be wheel balance, etc. The hum & vib @ 80 could be wheel balance, wheel bearing, cvj, etc. The rough idle could be due to a lot of things: injector(s), vac leak, warped/bad intake manifold leaking antifreeze into the engine (3800), dirty throttle plate, dirty bad maf/mat/iac, and a bunch of other things. Probably NOT ign.module, coils, or trans. Check those out first and let us know what you find. Paul.

Talked with a mechanic friend who said the idle vibration may be a harmonic balancer? And that the 80MPH hum may surely be a wheel bearing (tires are 2 months old and vibration was present before the new tires). I'm taking it to him tomorrow for a thorough once over. I'll let you know what it turns out to be.