I have a 94 Grand Am GT with the 3.1 V-6. Amoung the many other problems I've had with this car, The one major problem it was using way to much gas. The engine idled erratecly, stalled and would die if I did not keep one foot on brake pedal and one on the gas. All the spark plugs were carbon fouled. Well after spending so much money for nothing I found out all 6 injectors were firing at the sametime. Someone told me bad timing. SO I bought a new timing chain, and gears. (btw, it was total hell fixing that). After I finally got it all back together the car runs much better now. BUT while driving the car starts shaking when it is in 5th gear. If I let off a second and give it gas at or above 2000 rpm's it stops, when I let off alittle the rpm's drop down to 1500, and it shakes again. If I stay below 55 like around 53 it rides fine. Any idea's what the problem could be? Possibly the lock out switch to the torque convertor? Also if I disconnect the TPS it does not shake at 55 or above, but it shifts from 1st to 2nd to quick, and poor power. I know the TPS also partially controls the shifting of the transmission. Thanks for any help given.

Davy Rocket

if you disconected the TPS and the bad idle went away, I'd say thats what was causing that. Its a cheap(er) fix to try first.

But the 55mph shake could be the torque conv. , but it could also be a/an engine mount or trans mount ready to break or broke leting the engine jump around at higher rpms.

I've already replaced the tps along with a map sensor, 3 new ignition coils, and the icm, wires, plugs. So if it is the torque convertor, it would be the tcc switch? I've read I can disconnect it, but I do not know where it is located. The erratic idling was still there after disconnecting the tps, its the shaking that went away. Thanks for the reply.

Davy Rocket

tire balance?

tire balance is another possibility on the 55mph shake. I used to hav a 61-64mph shake, tried everything, new tires, rebalanced, nothing worked. Ended up replacing the CV joint and i hav no more shake, just another thing you might consider.

Here's the thing...When I disconnect the throttle postion sensor (tps) the shaking goes away, but shifts from 1st to 2nd to quick..Lack of power. I reconnect the throttle postion sensor (tps) the shaking comes back. I don't think tires, cv joints or any other front end parts of the car has anything to do with it. When it shifts from 3rd to 4th and the rpm's drop below 2k is when it starts shaking at 55 or above. I let off the pedal, then give it more gas right above 2k, the shaking goes away, but then drops back to 1800 to 1500 rpm's and shakes again.

Davy Rocket