I have a 2001 pontiac bonneville se with the 3800 gen 2 engine. I started to feel a vibration at idle and discovered a bad front transmission mount( oil filled). I replaced it. But now the vibration is becoming worse. Once I begin to drive, the vibration disappears. Its only at idle. Reverse seems to be worse than drive. I've checked the motor mounts and they appear to be in good condition. I've tried to remove the belt and run it, but the vibration is still there. If I hold onto the engine while its idling, its pretty rough and smooths out once it hits over 1500 rpm. So, Im not sure if its in the transmission, or if the engine is running bad. It does run fine though without any signs of misfire.
This is what I have changed recently.
front transmission mount
rear transmission mount
water temp sensor
gas evap canister solanoid.
spark plug and wires.
if anyone has any ideas as to where to look. It would be appreciated. Like I said. It only really vibrates at ilde. Thanlks.