99 Malibu LS 3.1 107,000 miles: hi idle RPM

From time to time my Malibu idles at 2000-2800 rpm. Like, when I drive in the city I may have to ride the brake to keep within the speed limit. When I shift to neutral as I drive, the RPMs really climb. My shop has replaced the air idle control valve and cleaned up the throttle plate. Was good for one day, then it began revving up again. I think replacing the AIC valve was a waste of money? Also, the 'service engine' light is constantly on; the code is 0442. Replaced the gas cap. When the code is cleared it comes back after a couple of starts. Any thoughts would be appreciated.

I have an 01 3.1, and at the time had about 125K on it. I had the same issue, and after I cleaned the IAC, seemed to solve it. The issue kept coming back, and I replaced the IAC.....only to have it happen again a few months later. I replaced it again, and the third IAC actually fell apart in the engine.

I replaced with OEM, and haven't had an issue since. Did you use OEM, or replacement?