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1991 Ford F-150 hard cold start, rough idle, hesitates under

Tiny
LEWISCYPHER
  • MEMBER
  • 1991 FORD F-150
Engine Performance problem
1991 Ford F150 6 cyl Four Wheel Drive Manual

I have a question, on the KOER test what would cause it to throw a 411 code, cannot control rpm during KOER low RPM check.
Tuesday, October 27th, 2009 AT 11:59 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Hi lewiscypher and TY for the donation

Your probable causes:

Improper idle air flow set.?
Vacuum leaks. --> Checked
Throttle linkage binding. --> Not binding
Throttle plates open. --> Not open
Improper ignition timing. --> Timed
Idle Air Control (IAC) solenoid contamination. New
IAC circuit short to ground.? Don't have a breakoiut box
Damaged IAC solenoid. --> New
Does engine Idle speed appear normal? --> About 850-900
Yes -- Remove IAC solenoid and Inspect for contamination. If contamination is present, determine if solenoid is a type that can be cleaned.

If Diagnostic Trouble Code (DTC) /symptom is still present, replace IAC solenoid.
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Wednesday, October 28th, 2009 AT 6:39 AM

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