Uneven rough idle

Before anything else do the "easy" stuff that has been recommended to you.

Clean MAF sensor (there's a thread on this on the forum).
Clean throttle body. Make sure to clean the Idle Air Control valve and IAC passage! Do NOT press on the pintle... Hopefully someone can let you know the reset procedure if there is one because I can't remember it and it's way too cold and late for me to go look for my manual.
Check plugs (replace if necessary)
search for vacuum leaks. Note: if your intake manifold gasket has never been changed, it IS leaking and may cause a vacuum leak. Change it.
R&R plug wires (or check them if you know when they were last done)

R&R fuel filter

Then, I would strongly recommend doing a Motorvac treatment, even if you find the cause of your rough idle. If you don't this very well may solve it.

Before spending money on getting your injectors cleaned, PLEASE find a shop that does Motorvac fuel system cleaning. There's a thread about it in the info subsection, but there are no shops listed for your State. Make sure it is the Motorvac name brand. This can solve seemingly impossible drivability problems.

If the tach shows a rock steady ~ 700 RPM but the motor is bopping around, your mounts are gone.

Actually, I replaced my motor mounts at around 100,000 miles and am about to do it again. With 190K on yours I'd guess they are toast.

The other items (clean the MAF sensor, clean the throttle body) are great preventive maintenance; so is motorvac treatment; should plan to do them.

...so tell us Josh what are you doing about this idle problem?

Albertj

hotrod58 wrote:

My SC 97 Riviera has 191,000 and has a new supercharger on it (previous owner was a lawyer). When you are at a stop light the car idles to about 700 but its a rough idle. Car had a complete inspection but I am wondering what would cause this in my Rivy? Is it just the way supercharged 3.8's are?

Is the idle rough in both Drive and Neutral?