idiling issue
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idiling issue
Hello I recently bought a 90 bronco xlt 5.8 I can't get it to idle above 600-650 sometimes it drops lower and almost stalls. I changed timing chain,plugs cap, rotor,standard tune up things but can't seem to figure this out we adjusted the idle screw and will do to about 800 for about five minutes then go right back down....please any help
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Assuming you are dealing with a fuel injected engine, that is NOT an idle adjustment screw. Adjusting it to increase idle RPM's will only cause you greater headaches over time. Your best bet is run both a KOEO and KOER test to determine where the problems truly lies and then to reset the throttle plate stop screw (the one that has been "adjusted"). RUN THE KOEO TEST FIRST! Otherwise the reset procedure will clear any fault codes that may be present that will indicate the true source of the problem.
NOTE: Codes 12 and 13 or Codes 411 and 412 are indicative of a disconnected or failed IAC. If these Codes exist prior to following the procedure below, you might as well check the electrical connection or replace the IAC all together before you go any further.
To reset the throttle plate stop screw you will have to disconnect the IAC. This will generate a fault code that will need to be cleared before running the KOEO and KOER tests.
Resetting the throttle plate stop screw:
1 - Start and run the engine until it reaches full operating temperature (or for at least two minutes with the RPM's held above 2000).
2 - Shut the engine down, disconnect the IAC at the electrical connector on the driver's side of the throttle body. (there are photos of this all over this site).
3 - Restart the engine and carefully back the throttle plate stop screw out until the engine sputters and dies.
4 - shut the key off and disconnect the battery for about 5-7 minutes. (this will clear the computer's memory of the fault code generated by having the IAC disconnected).
5 - Reconnect the IAC and restart the engine.
6 - Repeat steps 2 through 5 to verify the reset of the throttle stop plate is no longer affecting the idle.
NOTE: Codes 12 and 13 or Codes 411 and 412 are indicative of a disconnected or failed IAC. If these Codes exist prior to following the procedure below, you might as well check the electrical connection or replace the IAC all together before you go any further.
To reset the throttle plate stop screw you will have to disconnect the IAC. This will generate a fault code that will need to be cleared before running the KOEO and KOER tests.
Resetting the throttle plate stop screw:
1 - Start and run the engine until it reaches full operating temperature (or for at least two minutes with the RPM's held above 2000).
2 - Shut the engine down, disconnect the IAC at the electrical connector on the driver's side of the throttle body. (there are photos of this all over this site).
3 - Restart the engine and carefully back the throttle plate stop screw out until the engine sputters and dies.
4 - shut the key off and disconnect the battery for about 5-7 minutes. (this will clear the computer's memory of the fault code generated by having the IAC disconnected).
5 - Reconnect the IAC and restart the engine.
6 - Repeat steps 2 through 5 to verify the reset of the throttle stop plate is no longer affecting the idle.
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coleaclark
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