Bad Vibrations

[Bwana]

Here's the symptoms...

Pronounced pulsating vibrations around 50 mph in 3rd, practicly diappears if I shift into 4th. Very little vibration detectable in 4th. I can feel a little vibration in both 1st and 2nd but not near like 3rd. They all seem to occur around 2-3k rpms under light throttle. The car has new (500mi) 215-65-15 Yokohama AVS db S2 tires rated 95V, but had the same symptoms with lousey old tires too. Engine idles a little rough and seems to be a little high at 11-1200 rpms (idle screw is all the way out but this is as low as it goes) but feels very smooth in gear and under load, about 700 rpms at idle w/o a/c. Any ideas? BTW, new plugs, all injectors ohm good and MAF and throttle body recently cleaned. Thanks!

[maxnix]

If you have a discernible vibration at 50 mph in 3rd and 70 mph in D, then it is the rear transmission mount failing. May be other contributors also.

[cyclohexanol]

Mine also vibrates like crazy at around 40-50 and then again at 70 right around 2-3k rpm. (Possible dumb question) Is there a way to check the rear transmission mount to see if it's failing? And if it is failing, where would be the best place to get a new one? I'm guessing Joe at scottsdale? I would love to fix the vibration :/

[maxnix]

Call Joe and get the exhaust hanger bracket and replace it at the same time. If it is more than barley noticeable, you are wearing other drive train components at an accelerated rate.

1" of deflection is quite noticeable in driving, but difficult to observe by viewing the support.
Modified by maxnix at 3:18 PM 10/9/2004

[Q451990]

Engine idles a little rough and seems to be a little high at 11-1200 rpms (idle screw is all the way out but this is as low as it goes) but feels very smooth in gear and under load, about 700 rpms at idle w/o a/c.

Maybe a type-o, but out is higher, in is lower. Turn the screw all the way in (clockwise), then back it out 2-2.5 turns... If everything is clean you should be at about 650RPM.

High idle may also be incorrectly adjusted throttle cables. There should be a couple mm. slack in them when the car is fully warmed up. If they're too tight they'll have a tendancy to bind. You want to get this corrected since you're beating the transmission pretty hard putting it into gear at that idle speed.

Would you describe the idle problems as a "bouncing" feeling at idle? If so I'd suspect a dead cylinder (probably due to a bad injector). They can ohm fine and still be clogged. You might want to work on the idle problems and then get a power balance test to see what's going on... it may be time for an injector flush.

Good luck!

Heath

[Bwana]

I'm sorry, you're right, typo on the screw. I've been thinking pretty seriously about getting this thing down to the dealer and getting a consult/diagnostics done on it. It wouldn't suprise me a bit if the injectors needed cleaning. I'm not sure if I'd quite describe it as the dead cylinder feel, but at 1200 rpms that could be it. I was also wondering about the possibility of a vacuum leak? Where's the more common places for one to turn up? Sound reasonable?

[HeavyDuty]

I have a cyclical vibration in 3rd around 30 mph, disappears in 4th most of the time.

I know my pinion bearing is bad from a bad driveshaft, which has been replaced.

My trans mount looked good when doing the trans a year ago.

Personally I'd be surprised if it wasn't driveline related. Just a guess, I haven't had time to fool with the diff yet.