Have a 2001 GC limited nothing but a problem child (Just Expect Every Problem) anyway on cold start up and somtimes when it is warm as well but not as often. When first starting for the day revs to around 2500 RPMS an then goes down, when warm at a idle in park or at stop sign idles arounf 500-600 rpm then flares up to about 1100 or so and goes back and forth. No codes at all and when it revs to around 2500 rpms it smells like raw gas. I have no fuel leaks anywhere, decided to look at over head council as well when driving somtimes the same smell but the rpms are normal. when driving the instant mpg do not change thinking that if it was running rich my instant miles would droup dramatically. I am thinking the tps but i am not sure.
Try leaning out the throttle body and the idle air control valve. I'm thinking more the IAC valve than anything, because when you stop, it's that that takes over from the throttle body in getting air into the engine
Clean it thoroughly though and don't get any cleaner on the actual sensor.
If that doesn't work then it could well be faulty sensors, either the TPS or the IAC. Easy fix, just plug and play. I'm not sure what's causing the gas smell though
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