BHarvey -
This is similar to what Piwoslaw said ...
I think that's the Idle Air Control valve (IAC) in action. It's a pintle valve that is controlled by the ECU/PCM to increase/decrease the idle as needed. I like to think of it as a computer controlled choke. When the engine is cold the IAC is used to raise the RPM until the engine warms up :
http://www.2carpros.com/articles/how...ol-valve-works
Quote:
|
An IAC (idle air control) motor is designed to adjust the engine idle RPM speed by opening and closing an air bypass passage inside the throttle body. The cars computer or ECM (electronic control module) receives information from various sensors and will output signals to adjust the IAC motor in or out to adjust engine idle speed by controlling engine idle air. ...
|
At high MPH, the ECU/PCM decides to keep the RPM higher in preparation to rev-match with the next gear. At least that's what I think Piwoslaw is describing.
A proposed solution to the IAC is to intercept the IAC control wiring. The idea is to disable the IAC with a switch at driver discretion. You don't want to fully disable the IAC because a really cold engine is hard to drive. However, some people have tried this. They wait until they have a nice low idle and disconnect the IAC. From what I understand this should leave the IAC in it's current position.
You will find the IAC built into your throttle assembly.
Can someone chime in and correct me if/where I am in error?
CarloSW2