First, with the engine cold, start it, wait 1-2 minutes and feel the EGR valve. It should not be hot. If it is, the valve is stuck open, replace it. To test further, follow this procedure:
Install a tachometer on the engine.
Detach the engine wiring harness connector from the Idle Air Control (IAC) solenoid, it's on the side of the throttle body.
Disconnect and plug the vacuum supply hose from the EGR valve.
Start the engine, then apply the parking brake, block the rear wheels and position the transmission in Neutral.
Observe and note the idle speed.
If the engine will not idle with the IAC solenoid disconnected, provide an air bypass to the engine by slightly opening the throttle plate. Do not allow the idle speed to exceed typical idle rpm.
Attach a hand operated vacuum pump to the EGR valve vacuum port. Slowly apply 5-10 in. Hg (17-34 kPa) of vacuum to the EGR valve. You should see movement of the EGR valve stem.
If the idle speed drops more than 100 rpm with the vacuum applied and returns to normal after the vacuum is removed, the EGR valve is OK.
If the idle speed does not drop more than 100 rpm with the vacuum applied and return to normal after the vacuum is removed, inspect the EGR valve for a blockage; clean it if a blockage is found. Replace the EGR valve if no blockage is found, or if cleaning the valve does not remedy the malfunction.
Tuesday, May 29th, 2007 AT 9:26 PM