Idle Speed

Idle speed is controlled by PCM and idle speed control air by-pass valve on all engines. On most models, engine idle RPM is fixed and cannot be changed by standard adjustments. A scan tester must be used on these systems because control strategy and idle speed specification are controlled by PCM. See IDLE RPM SPECIFICATIONS TABLE .

Before performing idle speed adjustment procedure, complete a thorough basic inspection and self-test (KOEO, KOER, Continuous Memory self-tests) to confirm operation of sub-systems contributing to idle speed control. See QUICK TEST in appropriate article in the ENGINE PERFORMANCE section:

TESTS W/CODES - EEC-IV (4.0L) (for Aerostar & Explorer)
TESTS W/CODES - EEC-V (4.0L) (for Ranger)

IDLE RPM SPECIFICATIONS

Application

RPM

4.0L

⁽¹⁾

⁽¹⁾	Idle speed is computer controlled and is not adjustable.