Over reving on start up
make sure all the connectors are on the throttle body and nothing is binding. Jeeps have a service bullitin about something like this. Try removing the IAC and clean the pintal area or replace the IAC. I have a 93 wrangler and I have had this happen to me. I cleaned it and it worked. Try disconnecting the battery for a few minutes then try it again. This will reset the IAC to MIN. If this allows it to start at a lower RPM then you Isolated the problem. Try tappping on the IAC also. It may be sticking. Either way if anything make a difference then you will prabable need An IAC.Make sure you have no vacuum leaks anywhere. A vacuum leak will hold the idle higher also and the computer will close the IAC as far as possible to compensate.
Heres why you have a high RPM
When you start the car if you have a stuck open IAC or vacuum hose leak the O2 sensor will see this extra air and add fuel to compensate to maintaim a 14.7 to 1 ratio but also the computer will see your foot is off the gas and the throttle position switch is closed. Under this condition the computer will want a precalibrated RPM which is between 660 to about 750 rpm +or- some. It will close the IAC till it reaches this level.
Jul 14, 2009 |
1995 Jeep Wrangler