1995 Chevy Impala Shifting

RATLIFFD

MEMBER
1995 CHEVROLET IMPALA
V8
2WD
AUTOMATIC
158,254 MILES

Hello and thanks for having a website and radio show. I have changed my TPS approximately twice in 3 years. One time I had to change the wiring harness that attaches to the TPS. I also had transmissions issues that Aamco in Jacksonville, NC repaired, good job. Well, I need your expert advice so transmission issues won't return. Can you tell me why is it that when I turn on the AC the TPS/Shifting (1st to 2nd gear) gives me issues. I believe that the electrical /TPS issue is why I had to get transmission work. Should I get another PCM because the local auto electric shop told me that they are 98% sure that is the problem.

3 Replies

ERNEST CLARK

MECHANIC
1,730 POSTS

It's very unusual to have to replace a TPS twice in a matter of a couple years. Those parts last a pretty long time.

The A/C compressor puts a load on your engine when turned on, and your computer compensates for that by changing ignition timing, fuel delivery, and in some cases the shifting points of your transmission. (Higher or lower r.P.M.S)

With the age of your vehicle, and the problems you describe, it is very likely that your computer is failing. When computers begin to go, the frequently cause unexplainable problems. Only an experienced tech with good diagnostic skills will have the know how to eliminate other possible causes.

Finally, even if you trust the mechanics who advised you replace your computer, take it to another shop for a second opinion.

Not that your regular mechanic is dishonest, but you'd be surprised at the different levels of experience amongst mechanics and the different advise you'll receive. And you'd definitely want to make sure your computer is actually faulty before you replace it, right?

I hope this helps.