Ranger 2WD L4-2.3L VIN D (2001)
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Engine idle at approximately 650 RPM
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Engine temperature should be at least 190° F
(88° C)
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All accessories and the engine cooling fan should be off
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Steering wheel in the center position
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EGRVR and EVAPDUTY CYCLE are zero
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Short and long term fuel trims less than 15%
NOTE
IT IS USUAL TO SEE THE IAC DUTY CYCLE VARY BY 1% TO 2% OVER SEVERAL MINUTES.
NOTE
IT IS EXTREMELY IMPORTANT TO CHECK THE IAC DUTY CYCLE WHEN THE RPM IS AT 650 RPM. EVEN 700 RPM IS TOO HIGH
FOR CHECKING the IAC VALVE DUTY CYCLE UNDER THESE CONDITIONS. IF THE RPM IS OVER 650 RPM, MOMENTARILY
OPENING AND CLOSING THE THROTTLE AND A SHORT EQUILIBRATION TIME WILL LOWER THE RPM.
At stabilized engine speed and temperature, verify that the IAC duty cycle is between 27-36% with no purge flow (EVAPV duty cycle is 0%).
If the Duty Cycle is out of specification, proceed with the following steps:
1.
Ensure there is no purge flow.
2.
Verify PCM harness integrity by performing a wiggle test on the harness while the engine is running and observe the IAC duty cycle and engine
performance. Should abnormalities be observed, repair the harness as required.
3.
For an IAC duty cycle high concern, unplug and plug in the IAC power connector several times. If the duty cycle remains high, replace IAC valve.
4.
For an IAC duty cycle low concern, there may be an intake air leak. See the below IAC diagnostic service tip for DTC 1506 and other high idle
concerns.
NOTE
IF THE ORIGINAL IAC VALVE WAS WITHIN DUTY CYCLE SPECIFICATION OR THE DUTY CYCLE REMAINS OUT OF
SPECIFICATIONS AFTER IAC VALVE REPLACEMENT FURTHER DIAGNOSTICS ARE REQUIRED TO ADDRESS THE CUSTOMER
CONCERN.
Use the following Supplemental Information for 4.0L SOHC Engines In the Ranger, Explorer, Mountaineer, Explorer Sport and Explorer Sport Trac.
If no DTC's present check the following items in this order before examining the IAC valve:
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BARO Hz reading - Refer to Barometric Pressure Chart listed in this TSB
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Battery and fuse box power lead
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Ground wire attachments
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Wiring (wiggle test)
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PCM voltage
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Vacuum leaks
Examine AC valve under these conditions:
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PCM updated to the latest available calibration
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Transmission in park
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Warm stabilized vehicle with engine temperature at least 190° F (88° C)
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All accessories and cooling fan sh6uld be off
