hi i have a pontiac grand am gt 96 and when my motor is idling the car shakes?can anyone help thanxs?

Question

i changed air filter every year or so and the plugs and wires like 2 yrs ago

Answer 1

If the shaking goes away when you start driving, have the motor mounts checked. If it is 3.1 with a rough idle, pull your air intake tube off and see if the upper plenum inside the throttle body is builtup with carbon. If it is a 2.4 engine, pull the engine cover off and see if the DIS coil inside is tracked with black scorch marks. These get very hot inside the engine and jump fire right through the DIS assembly.

Answer 2

it sounds like you may have a dead cylinder at idle.

try this. Start your car, let it idle so you have the shake. Put on a pair of rubber gloves (this is important unless you don't mind getting a little shock). One cylinder at a time pull the plug wire off so the spark no longer gets to the plug. If it shakes worse, put it back on. Do this for all of the cylinders, one at a time. When the idle remains the same and you have one wire off you now know which cylinder you're dealing with.

THIS problem can be one of two things. not enough fuel at idle (is it fuel injected? run some injector cleaner through a couple of tanks of gas) or a fouled plug. Pull the plug and inspect it. If the porceline (the part thats white when the plug is new, right above the electrode) is a color other than chocolate brown then you may have a bad plug, a bad cylinder (like a valve, valve guide, rings) or if there wasn't any spark you may have a bad wire.

It can be many OTHER things, but this is a simple (free) test where you can start. Your plugs should be changed about every 10 or 12,000 miles unless your car has the new never replace plugs. Then they should be replaced at about 50K miles.

Good luck.

RE your engine mounts, like someone else mentioned. You won't normally get a shake out of the car at idle with a bad mount, but you can check them this way.

The mount that usually goes is the one that holds the engine DOWN. You can check this by having someone you trust with your life start the car, put it in gear (with the hood up) and give it a little gas to see which way your engine torques (which side raises up). Shut the engine off, put the car on ramps or stands (leave the engine off). Find the engine mounts, jack up the engine (put a block of wood under the pan and use a floor jack) about an inch or two at most. Inspect them. If there are ANY tears in them, or flaws (should be solid rubber with no flaws) replace them, expecially the one that gets PULLED on by the engine torque. It's pretty easy. But engine mounts usually last for a long time (unless you race around alot)

Good luck.

Answer 3

Change your plugs every 2 to 3 months,But it sounds like it might be a motor mount.

Answer 4

Vacuum leak, or loose spark plug wires, or fouled spark plugs, blown head gasket, stuck valves, faulty EGR valve....

It could be a whole bunch of things ............

Answer 5

You may have a bad injector or injector wiring. Try unplugging individually and see which one does not change.