97 LeSabre vibration

Hello experts,

I've got a 97 Lesabre with about 100,000 miles. Between 55 and 75 mph under light load, level ground and / or slight grades, I get a vibration almost like going over rumble strips. It's important to note that if I tap the accelerator (or let up on it), it immediately stops but will come back shortly....or maybe not for another 5 minutes. I've never noticed it at lower speeds. Does not happen going downhill. It happens with cruise on or off, A/C on or off. I've replaced all tires, I was told there was a bad wheel bearing...had it replaced with no success. Dealer has replaced the EGR valve, injectors, wires, plugs, used injector cleaner, fuel filter. A front end inspection turned up nothing and there were no codes / no check engine lite. Very frustrating and any thoughts would be most appreciated.

Thank you in advance,

Jim

Welcome to af, this can be caused by the trans lock up convertor slipping. To find this the car must be road tested with the condition occurring and being scanned with a trans function scanner, a good tech can pick out slippage errors in the lock up operation of the trans. A bad tps can slso cause the tcc to cycle on and off rapidly , this is less likely, but should be considered in the diagnostic procedure. It would seem the dealer, when experiencing the problem should be able to pinpoint this condition. How about all the money spent and no resolution?

Maxwedge,
I had a similar problem with a tps on a Nissan...very similar symptoms however the vibration was much more severe and over a wider range of speeds. This is a suspicion on the buick. I noted the accumulating costs today at the dealer and was hoping to corner a tech into riding with me for 30 minutes or so but they still want to charge. I guess time is time so I'll have to pay. So you feel that it's narrowed to these 2 items? The problem with the tps is that it can only be replaced, not tested to verify. Correct? And yes, I'd like an 'old timer' tech. Any ball park ideas about costs associated with repair of either?
I'll post the final solution once identified. Thank you in advance.

Jim

Maxwedge,
I had a similar problem with a tps on a Nissan...very similar symptoms however the vibration was much more severe and over a wider range of speeds. This is a suspicion on the buick. I noted the accumulating costs today at the dealer and was hoping to corner a tech into riding with me for 30 minutes or so but they still want to charge. I guess time is time so I'll have to pay. So you feel that it's narrowed to these 2 items? The problem with the tps is that it can only be replaced, not tested to verify. Correct? And yes, I'd like an 'old timer' tech. Any ball park ideas about costs associated with repair of either?
I'll post the final solution once identified. Thank you in advance.

Jim
I gotta tell you when I ran a Cad/Olds service dept, if I did that much work to correct a problem that still existed I would be bending over backwards to help you out here. You need to speak to someone in charge there and let them know what is going on!

I gotta tell you when I ran a Cad/Olds service dept, if I did that much work to correct a problem that still existed I would be bending over backwards to help you out here. You need to speak to someone in charge there and let them know what is going on!

Could it be an axle or constant velocity joint? For the trans torque converter clutch varied problems, can't most service managers ID those problems pretty quickly. They're not new problems.

Talk to management. Maybe you need a different dealer shop. But that one owes you a fix.

Here's the latest. The dealer attempted to do a scan but said their scanner could not read from the car. They indicated that there must be some other problem causing this. They also noted that the trani fluid was a burnt brown color rather than the normal reddish pink. So, their final conclusion is that the trani needs to be rebuilt. My feeling is that I'll run it for another year rather than invest in a unit that may not be worth any more aggravation.

Jim

REPLACE THE FLUID and add a additive.. Cheap try.. It worked for me.
Its proubbly the TCC valve but this cheap advice might get you many miles down the road.

Maxwedge,
I took the unit to a reputable trani shop. They scanned it at no cost while driving and found a bad torque converter. The tech put in some gook that will possibly stop the shudder but recommends an overhaul....$1600 - $1800. Also noted that I can extend the life of the trani by not driving on the freeway. I think you hit it on the head. Thank you for your input. Now I need to make a decision.

Not to discourage you but I have had bad advice from even the experts. A bad ground on my VSS sensor caused the trannie to act wierd. The experts wanted to sell me a re-manufactured trannie. It was a real headache listening to the advice and not taking it but the results were nice. I fixed it for nothing.

COULD IT BE CHUGGLE?

Tapping the accelerator made me think of the TCC valve. I expect your feeling it more often during higher order shift changes on specific road conditions and on up hill grades.
Ive heard of the TCC valve going bad and causing what is defined by GM as "chuggle".. look up chuggle on trannies and see if it describes your problem and test drive it looking for signs. Basically it occurs mostly during higher shifting speeds (predetermined by the PROM) or engaging or disengaging the torqe converter lock. The TCC valve controls the lock in and out of the engine to the torqe converter for direct connect to save gas. It gets leaky and new trannie fluid can help with an additive that will softenl the valve parts. Ive also hear PROM program change can aleviate it for a slight loss in MPG.

If it occurs while hot sitting in the drive way reving up a bit holding the brake ... FORGET the above.

Good luck.