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While driving occasionally the idle will climb to 2000 RPM's when the clutch is depressed.  I can drag the RPM's down to around 800 through down shifting but when the clutch is depressed the RPM's will climb back to 2000.  It stays there for about 60 seconds and goes back to 800.  I've checked the throttle linkage and sprayed them with WD40 with no resolution to problem.  Please help.  

there are several things that it could be...

but you really need a scan tool to look at the various voltage signals from the sensors...

if you have vacuum operated power brakes... i would pinch off the vacuum hose to that for a test... see if it has a leak...  the power brake boosters have the ability to leak enough vacuum to cause this problem..

some of the other things it might be.. but you have to verify with a scan tool before replacing anything...


The idle validation switch (IDS) provides the PCM with a redundant signal to verify when the accelerator pedal is in the idle position. Any detected malfunction of the idle validation switch will illuminate the check engine light and cause the engine to operate at idle only.
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The Idle Air Control (IAC) valve adjusts the engine idle speed. The valve is located on the side of the throttle body. The valve is controlled by a duty cycle signal from the PCM and allows air to bypass the throttle plate in order to maintain the proper idle speed.

Do not attempt to clean the IAC valve. Carburetor tune-up cleaners or any type of solvent cleaners will damage the internal components of the valve.
TESTING

Fig. Fig. 1 The IAC can be monitored with an appropriate and Data-stream capable scan tool

Turn the ignition switch to the OFF position.
Disconnect the wiring harness from the IAC valve.
Measure the resistance between the terminals of the valve.


Due to the diode in the solenoid,  you may have to reverse the leads to get a reading..

Resistance should be 6-13 ohms.
If resistance is not within specification, the valve may be faulty.

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The Throttle Position (TP) sensor is a potentiometer that provides a signal to the PCM that is directly proportional to the throttle plate position. The TP sensor is mounted on the side of the throttle body and is connected to the throttle plate shaft. The TP sensor monitors throttle plate movement and position, and transmits an appropriate electrical signal to the PCM. These signals are used by the PCM to adjust the air/fuel mixture, spark timing and EGR operation according to engine load at idle, part throttle, or full throttle. The TP sensor is not adjustable.

The TP sensor receives a 5 volt reference signal and a ground circuit from the PCM. A return signal circuit is connected to a wiper that runs on a resistor internally on the sensor. The further the throttle is opened, the wiper moves along the resistor, at wide open throttle, the wiper essentially creates a loop between the reference signal and the signal return returning the full or nearly full 5 volt signal back to the PCM. At idle the signal return should be approximately 0.9 volts.

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what has to be found...   is it a mechanical problem... an air leak.    some hose loose... the brake power booster going bad...
a worn out idle air control motor has been known to cause this..

or is the computer commanding the idle air control motor to speed up do to sensor readings ...  

Did you find the solution to the run away idle problem?

80skeys