My van is idling very high. It ranges from 2800-3100 RPMs. I tried repairing many parts but the problem remained the same. For instance, I replaced the valve cover gasket, throttle body gasket, wires and coil, spark plugs and distributor cap. Also, the idle air control gasket is new as well as the upper intake gasket had a leak. I tried removing the idle air control and the RPMs would drop to a normal range. I figured that it needs to be replaced, but after plugging a new IAC, there was no improvement. I tested the IAC and it's been getting good voltage. I checked for vacuum leaks and there are none. What else can I do to fix this?
You need to disconnect the throttle cable from the throttle body to see if the idle comes down. If it does, you may have a misadjusted transmission downshift cable which is holding the throttle body open. If it still idles high then you may have a problem with the throttle body itself or the throttle position sensor. Have the vehicle scanned to see if there is any key on engine off and key on engine running codes. It should indicate a problem code to be diagnosed. If you would like, a certified technician from YourMechanic can come to your home or office, diagnose your idling issues and make necessary repairs.