Could be bad muffler bearings.
IF ITS JUST AT IDLE, CHECK YOUR IDLE AIR CONTROL VALVE IF IT HAS ONE.
By a real Car a$$wipe
Check idle adjustment (rpm) then check timing, then check for misfire-start there.
The most common reason for an engine not to start is a lack of fuel. A plugged air filter can cause and engine to idle rough or not idle at all.
You broke it. Way to go.
why does my vr commodore idle rough when at complete stop
Why does my 2001 kia sportage idle rough?
rough idle smell gas
The idle speed sensor tells the onboard computer how fast your engine is idling. The location of the idle speed sensor on the VW Jetta is on the actual throttle body.
a longer cam shaft will make a car idle rough
Try cleaning the EGR valve.
When the idle goes rough, you must idle the plugs. Else the car plugs roughly.