1994 Buick RoadMaster Station Wagon 350ci, with 75000 miles. While driving at speed, if trying to accelerate, the car will shake when it attempts to downshift just one gear. Does not happen when pushing the gas in all the way, but only when it downshifts one gear. It also happens occasionally when leaving a stop a stop, the car will shake, and barely accelerate, like it can't get into gear. I took it to a shop, and they couldn't get it to do anything, so I had them replace the torque converter lock up switch, but that still didn't fix the problem. Any suggestions?

Thanks.

The problem is, with an intermittent problem, it will be real hard to track down, the symtoms are anything from a plugged converter, check by rapping on the exhuast, hear any rattles? to the computer itself! Has the check engine light come on? With these symtoms it should have by now! Does the light come on with key in the on position? It should.

Thanks for the quick reply. For me the problem is pretty much constant, at least with the downshifting part. I have never thought of the converter, I'll take a look at that a little later. The check engine light has never come on. One of my friends suggested the electic shift switch, but I don't know if this car has one or not. I'll check the converter here in a few minutes and will repost.

Just a quick update, I went out, and tapped on the cats, and didn't hear anything rattling. Very glad to not hear anything. Also, when I flip the key to the 'On' position without starting the car, the 'Service Engine Soon' light comes on and stays on, but when I start the car, the light goes out. I'm not sure if this is expected behavior. I know when first started all of the lights should come on, but don't know about behavior if it just stays in the 'On' position.

Yes the light should behave as it is...

Ok...any other suggestions?