99 grand am 2.4l rocking back and forward in idle

when sitting in idle, the car will start to rock back and forward. i just recently had problems with the car misfiring so the mechanic replaced spark plug connecters, but the car still rocks back and forward and makes a nice low pitch noise out of the exhaust, almost like its a muscle car, dunno if that has anything to do with the rocking.
Could it be the spark plugs, or maybe even the idle sensor???

i am lost confused, need help big time!!!!

i had the same symptoms and it was my fuel pump once replaced it all was gone

What kind of engine? Quad4 misfiring usually the problem is the Ignition Coil Housing. If not the ignition coils and then the ICM.

IDLE is controlled by IAC (Idle Air Control solenoid) which is located on the throttle body. Try cleaning the IAC and the spot where the IAC goes in and test it. The IAC might be bad.

If you have not replaced the fuel filter for a long time then it might be time to replace it and test.

Hey i might be able to help you out... I drive a 99 Olds Alero with the 3.4

Once you start driving, does the bucking go away?

This just happened to me the other day...when i was idling, it would begin to buck back and forth, and the rpm's would jump from 500-750 and fluctuate around...

I took it in, and they said I had a slplit line leading into my intake.... After the diagnostic, parts, and labor, it was $85 to fix, and I havent had the problem come back yet... however, im not sure what the diag code for it was

hope this helps

jr. Gong