Help Idle Proublems
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Junior Member
Joined: Oct 2003
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Help Idle Proublems
Ok at idle mt car raises and lowers about 1300 rpm Like im slowly hiting the gas and slowly letting off ive changed my map sensor and my IAC i cant figure it out plz help it drives me crazy it started just in the morning when it warms up for about 10 min it stops i replaced the IAC 3 times with junkyard parts keep in mind my IAC costs $266.99 and only $6.00 at a junkyard and i dont know what else to look for.
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Joined: May 2002
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What you have is generally referred to as a 'Hunting Idle'. Here are some common causes of a hunting idle, and what you can do to check them:
Stuck or Binding Throttle Linkage - With the engine off, pull off the last section of intake piping before the throttle body. Have someone sit in the car and depress the throttle through its range of motion while you watch it. Make sure it opens and closes correctly, and take note of the position it sits in with no pressure on the pedal. If it's sticking or off at all, it may need adjusting. Now is also a good time to remove the throttle body and clean it if it's at all dirty.
Throttle Position Sensor - The TP sensor is a potentiometer that consists of a small metal wiper that slides over a thin carbon film. If that carbon film becomes worn, it can make the TP sensor give inaccurate readings over the 'worn' area. If you're worn around the idle (closed) area, this could cause the hunting. Short of finding. You can test the sensor quickly by reading the voltage it supplies to the ECU. It should be low, around 0.5V at idle (closed throttle), and it should NOT be bouncing around at all. If it's shifting, say between 0.4-0.6V, you've found your problem.
Vacuum Leak - Not much you can do to test this one except to stick your head under the hood and listen. If you're loosing vacuum somewhere, it can cause your idle to bounce a bit.
Those are the major causes. There are other potential sources of trouble like fuel pressure, compression problems, or ground-outs, but I would be looking at those three first .. 9 times out of 10 it's one of the three I listed (or a combination of lots). I would start by doing the first one I listed - clean and inspect your throttle body and linkage, and go from there.
Lemme know if you need more help.
Stuck or Binding Throttle Linkage - With the engine off, pull off the last section of intake piping before the throttle body. Have someone sit in the car and depress the throttle through its range of motion while you watch it. Make sure it opens and closes correctly, and take note of the position it sits in with no pressure on the pedal. If it's sticking or off at all, it may need adjusting. Now is also a good time to remove the throttle body and clean it if it's at all dirty.
Throttle Position Sensor - The TP sensor is a potentiometer that consists of a small metal wiper that slides over a thin carbon film. If that carbon film becomes worn, it can make the TP sensor give inaccurate readings over the 'worn' area. If you're worn around the idle (closed) area, this could cause the hunting. Short of finding. You can test the sensor quickly by reading the voltage it supplies to the ECU. It should be low, around 0.5V at idle (closed throttle), and it should NOT be bouncing around at all. If it's shifting, say between 0.4-0.6V, you've found your problem.
Vacuum Leak - Not much you can do to test this one except to stick your head under the hood and listen. If you're loosing vacuum somewhere, it can cause your idle to bounce a bit.
Those are the major causes. There are other potential sources of trouble like fuel pressure, compression problems, or ground-outs, but I would be looking at those three first .. 9 times out of 10 it's one of the three I listed (or a combination of lots). I would start by doing the first one I listed - clean and inspect your throttle body and linkage, and go from there.
Lemme know if you need more help.