Thanks for the post!
Well you're right, the unit is supposed to idle once it reaches its max pressure (120 PSI). The motor will typically dip down to about 1,250 RPM (it varies by engine of course) and should remain in idle until it's called for air again, usually around 90 PSI, which it will then kick in to high gear again.

If it dies at idle, I'd check two things:
1. Adjust the idle speed on the engine itself; usually this is a screw located near the carburetor.
2. Faulty Idle/Throttle Control Valve. This may not be kicking the engine to idle when it reaches max PSI. This part connects from the Pilot/Unloader Valve (large, hexagonal valve installed in the tank, the "brains" of the unit) to the engine governor. Find out if the line connecting the two is a cable (usually a metal cable in a black, plastic sheath) or if it's a hollow, plastic tube. It simply may not be actuating the throttle plate to kick it down to idle, or it just needs adjustment.

My bet is on the engine idle speed setting, though. You may want to simply take the carb apart, clean it very well with carb cleaner, re-install it, and adjust the idle screw (clockwise) until it doesn't stall out.

Hope this helps!
- MTR

I see, in this case I'm sure the engine throttle just needs to be adjusted, as it sounds like the Pilot Valve and Throttle/Idle Cntrl Valve are doing their respective jobs.

If you're not sure how, you can contact Briggs & Stratton directly at 800-444-7774 and I'm sure one of their techs can easily assist you.

Thanks again!
- MTR