Idle High

[lostlake]

My 2004 Malibu Response LXI with 250 hours on it occasionally idles high, above 12000 RPMS. Anyone no how to fix? Usually if I turn it off it will idle normally but not all the time. Seems to be getting worse. Has 340 Moonsoon Engine. Would appreciate any help. 

[justgary]

Could be a gummy IAC, bad TPS, vacuum leak, or even a bad ICM under the distributor.

I would start with a full tune up to see if that cures it.

[ROFF]

I thought I read somewhere around that year the ECM program had an incorrect high idle to compensate for the previous year where the engine stalled when put in gear.  
 

Fixed with a subsequent reflashing of the ECM.