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Old 06-14-2010, 02:02 PM
CUTiger CUTiger is offline
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Join Date: Jan 2010
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Default Re: engine stays at high revs when shifting / not in gear

Quote:
Originally Posted by FireRanger View Post
There is nothing electronic about the throttle on our trucks. Its a cable from the pedal to the throttle plate. When you let your foot off the pedal, the throttle plate closes immediately; there is no delay and no method for the engine to decide to keep it open a little longer. I suggest cleaning the throttle body and give all the linkage a good inspection. If something is sticking, you should fix that before you plow into a bus.
ummm what about the IAC valve? Its electronic and it opens a bypass to the throttle body, its my understanding that it could do this between shifts holding the rpms a little high for a short amount of time. Granted if this time is too short the IAC valve could be sticking.

Quote:
The IAC Module is used to adjust the engine idle RPM speed. The IAC Module opens or closes an air bypass valve (vaccume line) inside the throttle body. It is used to allow the engine to run at idle without stalling due to lack of air when the throttle body is closed (zero throttle input). When the throttle is lifted between a shift the ECU tries to adjust the IAC based on the information it is being provided from several different sensors. If ECU is told about a high RPM situation and a low or zero throttle input it tries to maintain the high RPM (even with zero throttle input) by fully opening the IAC Module to let in as much air as possible. If the IAC were to not open the engine would be nearly starved of air and the RPM would drop very quickly. The consensus is that this engineering solution helps to provide smoother and softer shifting on the up shift.
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Last edited by CUTiger; 06-14-2010 at 02:04 PM.
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