70K miles on car. Idle speed regualy fluctuates down and occasionally stalls both in Park & while driving at a stop light. Fuel pressure checked starts at 39 psig and jumps to a steady 60 psig. No engine fault codes. Any ideas what else to diagnose?

 

Thank you for those who have replied to this post. Checked some potential components such as coild for affect with heat gun but did not affect idle/stalling. Using Actron CP9150 scanner noticed IAT temp went up with closed hood. As temperature approached 130 and went above deg. F. idle became rough. Found poor air filter canister sealing. Reinstalled air filter & appears to have corrected itself.

 

Your Vehicle: 2003 Ford Taurus V6-3.0L DOHC VIN S


Vehicle » Powertrain Management » Fuel Delivery and Air Induction » Idle Speed/Throttle Actuator - Electronic » Description and Operation



Description and Operation


IDLE AIR CONTROL valve

The idle air control (IAC) valve assembly controls engine idle speed and provides a dash pot function. The IAC valve assembly meters intake air around the throttle plate through a bypass within the IAC valve assembly and throttle body. The PCM determines the desired idle speed or bypass air and signals the IAC valve assembly through a specified duty cycle. The IAC valve responds by positioning the IAC valve to control the amount of bypassed air. The PCM monitors engine rpm and increases or decreases the IAC duty cycle in order to achieve the desired rpm.

On applications with air-assisted injectors, the IAC valve also supplies a small amount of air into the path of the fuel injectors. The jet of air causes an increase in fuel atomization at low speed and light load conditions.

NOTE: The IAC Valve Assembly is NOT ADJUSTABLE and CANNOT BE CLEANED.

The IAC valve (part of throttle body assembly) has an internal diode on some applications. If the internal diode is measured in crossed terminal position with a digital multimeter, there will be an incorrect or negative reading. It is important that the mating component and harness connectors are correctly oriented. Diagnostic procedures emphasize this importance.

The PCM uses the IAC valve assembly to control:


•No touch start
•Cold engine fast idle for rapid warm-up
•Idle (corrects for engine load)
•Stumble or stalling on deceleration (provides a dash pot function)

I had same problem and this took care of it.