2002 grand am 4 cylinder rough idle and rough running

The basics for a rough idle, check for a leak of some kind, fuel--egr--vacuum leak. Check and clean anything to do with idle air system.
How long since a tune-up?

Check for vacuum leaks.
Do It Yourself Diagnosis and Repair

your idle valve may be dirty or needs replacing would check this as it controls idle. sits on the intake with wires coming out of it.

Rough idle is a very common problem on 4 cylinders, but I believe the 98 Regency has a 6 cylinder in it, right?

Sometimes the coil packs get iffy, and sometimes the EGR Valve gets a leak in it causing a rough idle.

When the accelerator pedal is depressed, it can change things so that the engine seems to run smoothly.

However, I would look for codes to see if anything intermittent is occurring in the engine that may need attention.

The OBD-I scanner can help to diagnose the problem, if anything is out of specifications on the engine in question.

The owner will have to find a technician that has such a scanner.

ROUGH IDLING CAN BE CAUSED BY VACUUM LEAKS.LIKE THE INTAKE MANIFOLD GASKET.OR VACUUM LEAKS FROM HOSES.LOW COMPRESSION CYLINDERS WITH BAD VALVES.LEAKING EGR VALVE GASKET.DIRTY CLOGGED FUEL INJECTORS WILL CAUSE ROUGH IDLING.

hi dispite all your hard work the error says you have a missfire /random cylinders hope this helps if so give the answer a rating please thanks pete

It sounds like a few different things or a combination of more than one.

1. The EGR valve
2. The catalytic converter
3. The mass airflow sensor

it sounds like you have a injector leaking down into one of your cylinders so it is flooding out a cylinder thus runs rough and long cranks.

Engine light on? sounds like EGR valve the cross pipe from EGR to air intake plugs causes them to idle rough if eng light not on soon it will surface! good luck hope this helps!

a faulty fuel pressure regulator might be the cullpret too much fuel will also throw a misfire code