Hello, sounds like to me it may be the idle speed control. Sometimes when it is surging can you shut the car off, wait a second, and start it back up and it idle okay? Here is the below on what it does.
This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of air which bypasses the throttle valve via IACV-AAC valve. The IACV-AAC valve changes the opening of the air bypass passage to control the amount of auxiliary air. This valve is actuated by a step motor built into the valve, which moves the valve in the axial direction in steps corresponding to the ECM output signals. One step of IACV-MC valve movement causes the respective opening of the air bypass passage. (i.e., when the step advances, the opening is enlarged.) The opening of the valve is varied to allow for optimum control of the engine idling speed. The camshaft position sensor detects the actual engine speed and sends a signal to the ECM. The ECM then controls the step position of the IACV-AAC valve so that engine speed coincides with the target value memorized in ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warm up, deceleration, and engine load (air conditioner, power steering and cooling fan operation
Also, with throttle body cleaner, if you spray it into the TB with the engine running does it start to surge?
Let us know.....
Friday, October 10th, 2008 AT 11:23 PM