2003 Limited V8. I bought it new. Since day one the idle has been slightly low when running with the AC off. It's just low enough to cause some minor stumbling, but not low enough to be unusable. With the AC on; the idle is perfect. I would like to raise the 'AC off' idle speed by about 100 RPM.
Any help on how to do this would be much appreciated.
Note: when I lived in South Florida; there was not much opportunity to run with the AC off. It's a little cooler where I am now.
There is no way to mechanically adjust idle on modern fuel injected/computer controlled engines. This is all part of OBD2/emissions regs, since idle speed impacts tailpipe emissions; especially when the engine is cold. Technically, many throttle bodies do have an adjustment screw on them, but DON'T mess with it. It is NOT for what you want to do, and messing with it, without knowing what you are doing, can cause lots of problems.
It sounds like you might have an IAC(idle air controller) valve that's on it's way out and/or partially clogged w/ carbon. You can try removing it and cleaning it first. If that doesn't work, replace it. If you aren't sure what that is, or how to remove it, then do a search on the forum and/or google. There should be a detailed how-to on here somewhere. Try searching for "IAC cleaning" (w/o the quotes). After you have done either of these steps, I would recommend resetting the Idle learn function of the ecm, in order to allow it to relearn the IAC settings/proper idle speed. You can do this by either disconnecting the battery for approx. 10 min, or you can use a scan tool to just reset this function. Pulling the battery will also erase your radio presets,etc..., whereas using a scan tool will not.
If cleaning and/or replacing the IAC does not give you the desired results; and assuming there is nothing wrong with your engine, then you might want to look into a flash programmer (SCT XCal3,etc..) Along with numerous other engine/transmission performance improvements, you would have the ability to adjust your idle speed electronically, via the handheld programmer,or you can have it adjusted within the tune. Call James @ Henson Performance about the tuner. he has done alot of the vehicles on here, with many excellent results.
