Shaking at Stop?

Question

1990 Pontiac Grand Am, Automatic Trans.

When driving, the vehicle runs smooth. When I come to a stop it will shake, not like a 12 on the rhictorscale, but it vibrates and its very noticeable. This probelm goes away if I slip it into neutral or park. It has done this since I have owned it, and the spark plugs and wires have been changed 3 times, regular maintainance kept up on, and not driven hard. Looking for suggestion on what this could be, because, frankly, I have no idea.

Answer 1

You can try whatever everyone else suggested but you should also check the obvious and check out your transmission and motor mounts. An easy way to check this is to pop your hood and put your foot on the brake pedal firmly put the car in drive and give it a little gas. DON'T let the car move and have a friend observe your engine/trans. and see if it raises up like it's coming out of your engine compartment. If one of them are broken then it will be very noticable.

Answer 2

You didnt mention the distributer cap and rotor..... change them also. If the car is carburated them the carb might need to be adjusted, the rich/lean mixture, if it is fuel injection then put some fuel injector cleaner in the tank.

Answer 3

have you checked your engine and transmission mounts,could be one is broken or loose,you say regular maintenance, does that include a through tune?if you brought the car second hand could be the previous owner installed a different cam shaft and your idle is as smooth as it will get..

Answer 4

check your idle speed

check your distributor cap and rotor

then check your fuel injection

also you never mentioned if the plugs are gapped correctly

Answer 5

transmission input shaft sensor is bad,is out side the tranny by the torque converter housing.
since ,You mention neutral and parking ok.
that eliminated the engine problems.

Answer 6

Where do you feel the shake?

If it is in the steering wheel while applying the brakes, your brake rotors are probably warped.

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