Transmission problem on 95 Lumina

I have a 95 Lumina with a 3.1
Today on my way to work something odd happened that i will try to describe as best i can given my limited car lingo.

The lock-up torque converter kicks in at about 80 km/hour when the engine is warm. When i got above that speed this morning it was like the torque converter wasn't able to properly engage. Instead it kept kicking in and out which resulted in a stumbling feeling in the engine. It did this for about 3 or 4 km on my way to work, then a little more on my way to the job site. After about 5km on the open highway it went away and didn't do it again.

I just got the car last week so i don't know if this is a new problem or something that was always there. In the week i have had it though, this is the first time i have noticed it.

Any ideas what this may be and what might be necessary to diagnose/repair it?

TIA There are several things that would cause the TCC to fall out of lockup. I would start checking things like the brake light switch under the dash which is at the brake pedal arm. Make sure it is adjusted properly and not broken. You might have to check it with a DVOM. A leaking TCC regulator valve in the valve body would cause it. A faulty TPS (Throttle Position Sensor) or even a temperature sensor would cause the symptoms you describe. The thing you need to do first is to have a scanner put on the vehicle and see whether the TCC locking and unlocking is being commanded by the computer. This will let us know whether the problem is electronic or hydraulic (Mechanical).

Good luck


transman Another thing that may or not be related came to mind when you mentioned the computer commanding it to occur. On my way to work that morning i had engaged the cruise control. Normally when you push the little spring loaded switch to the side, you accelerate until you let go and that is your new speed. But this time, when i released the switch, the cruise would disengage. At the time i thought that maybe when i released the switch it had bounced far enough back that it had momentarially gone to the off position.

Not sure if that is related at all and i did not try the cruise since. Well, think of it this way. What normally is supposed to happen when you are cruising down the freeway with the cruise control on and you tap the brake pedal ? The cruise disengages, correct ? Well, the Torque Converter clutch also electronically unlocks when you tap the brake pedal. With both of these problems occuring, I would concentrate my attention on the brake switch on the brake pedal arm. This is your common link between both of your troubles. Check and make sure the switch is adjusted properly. Check the brake pedal arm and make sure it is returning completely to its forward position. When you are driving, does your left leg tend to make contact with the brake pedal ?? Are you one of those people who brake with your left foot ?? Just a couple of other thoughts.


transman The car i have been driving for the last 6 years is a 5-speed and i'm not a left foot braker. I will take a good look at the brake pedal cause what you are saying about the brake pedal maybe not returning to the fully retracted position seems to fit with the available evidence. The cruise doesn't seem to be giving me problems as much but the torque converter only seems to act up when i am not using the cruise so it's hard to attach the two problems. Here were the symptoms I had......

When accelerating, the a/c would kick off, until up to cruising speed.
Didn't notice this until spring/summer of 04, but had shifting problems for far longer.
What it turned out to be was a vacuum leak somewhere in the a/c and vacuum reserve tank. 3 transmission shops could not figure out, all told need rebuild, but then not sure if it would cure problem.
My a/c guy found the leak, a/c works great, shifts like a new car(with 85k miles).
Owner, 1995 Lumina, 3.1 v-6 After reading a bit more about the car i tried very hard today to get a better "feel" for the problem. Although it happens at higher speeds and seems to be related to the torque converter (i.e. seems to shift). I think that may be more of a result of another problem.

What would a flaky fuel injector feel like?

It seems as though when it stumbles it just seems to happen quicker than the tranny can shift in and out of overdrive. Sometimes the "stumble" can feel like it is happening several times a second and is accompanied by a small loss of power. It doesn't feel like a miss, i had a miss once in my Corolla and it was very noticable, this is more subtle. It also only seems to occur at relatively light throttle (say 30% or less) but can occur at any time. It has happened when the car is cold and happened on the weekend after 2 straight hours on the highway.

I am starting to think this may be more engine and less tranny given the inconsistent history of the 3.1 fuel injectors (based on what i have read).