Help...

[93BlackZ28]

My car is idleing way too high, its like at 1500 rpm and i have no idea why. idk if its the cold or anything but it does this when i start it sometimes. and today i got on it and when i let off the rpm slowly went down and when i shut it off and start it, it still does this. If anyone knows anything let me know.

Thanks

[Jeff_in_Atl]

If nobody posts anything else, I would start by cleaning the IAC. http://shbox.com/1/iac3.jpg (thanks to Rob "Shoebox" and his website yet again). Maybe it is stuck open.

[Injuneer]

The idle speed is controlled by the IAC valve, based on input from the ECM. The ECM has a table of coolant temperature vs. idle speed. If it really is very cold, or if your coolant temp sensor is indicating an unrealistically low coolant temp, the idle could be higher than normal. The settings from my 94 stock program show an idle speed as high as 1,200rpm for an A4 with the temp at -40degF (what the ECM reads if the coolant temp sensor is not connected or burned out). At 24degF, the A4 idle speed is 1,000rpm (vs. 650rpm in neutral fully warmed up). In gear, the A4 should never idle above 800rpm.

The M6 is programmed to idle as high as 1,200 at -40degF, and 1,000 at 24degF (vs. 800rpm fully warmed up).

High idle speed generally means too much air is entering the intake. Throttle blades sticking open, vacuum leak, or an IAC valve that isn't closing down.

A "scan" of the ECM will show what the ECM is trying to do with the IAC counts in response to the excessive idle speed, and may point towards the problem.