Dealership could not fix problem....so I'm turning to all of you! When I let off the throttle, put manual trans. into N, the engine still rev's at around 2.5-3k RPM's for about 5 seconds and then notches it way down to normal. It will go from 3 to 1.5k then to normal idle. The RPMs go to a "normal" speed when engaged in a gear. For instance, when driving and changing from 2nd to 3rd gear, when depressing the clutch the Tachometer does not fall for the second it takes to change gears, it stays rev'ed, then once the clutch is released and the gear is engaged ,the RPM's are appropriate for the speed and gear.
The IAC valve was changed but this did not fix the problem . Do you think it could be the Throttle Position Sensor? It has been hot outside the AC was on initally but then shut it off and the problem still existed. The engine did not rev in the morning...it was much cooler. Thanks in advance
Nice problem statement.
But. Need to know the year and engine/trans you are running. The IAC controls the idle on a MAP system, but an air leak elsewhere from the IAC will allow for a high idle. On MAF systems, extra 'unknown to the MAF' air will cause a poor idle and hesitation, for instance . If you have ODB-II, you can read the commands to the IAC to know if the ECM is telling it to keep the idle up. I'd check for codes to make sure that the hi idle isn't trying to compensate for some other item that is malfunctioning.