Resetting the ECU

[Jeff Chambers]

The PCM does learn idle corrections. In fact, it learns them very quickly. However, the idle circuit is a very complicated system and affects driveability more than any other routine(s) IMHO. The biggest mistake that I see is people trying to set the idle up using the set screw, to some idle value that they think makes the car run better....say 850 in this case. However, the PCM has an idle setting for both nuetral and drive conditions (as well as decel/coast and others) that it is always going to try and achieve. For most calibrations, this neutral idle setting is in the 640-740rpm range. The computer will do whatever is necessary to get to this setting, including removing air, fuel and spark as necessary. So setting the stop screw for 850 rpm will cause more problems than it cures. The PCM learns idle quickly, but there are limits to the adjustments that it can make.