Controlled Idle Speed Check

NOTE: DO NOT attempt to adjust idle mixture and idle speed. Both are controlled by Electronic Control Module (ECM). Incorrect idle speeds are normally caused by dirty throttle plate or vacuum leaks. Ensure all vacuum components are functioning properly.

NOTE: Controlled idle speed and IAC count can be checked using scan tester. See CONTROLLED IDLE SPEED & IAC COUNT . Minimum idle speed adjustment can only be performed on 7.4L engines. See MINIMUM IDLE SPEED ADJUSTMENT .

Ensure no trouble code(s) are present, IAC system is okay, and ignition timing is correct. Block drive wheels. Apply parking brake. Connect Tech 1 scan tester to Data Link Connector (DLC). Put scan tester into OPEN mode.
Start engine and bring to normal operating temperature. Check for correct state of Park/Neutral switch on scan tester. Check if idle speed and IAC valve pintle position (counts) are as specified. See CONTROLLED IDLE SPEED & IAC COUNT .
If idle speed is not within specification, refer to TESTS W/O CODES - GASOLINE article in this section. Perform MINIMUM IDLE SPEED ADJUSTMENT .

CONTROLLED IDLE SPEED & IAC COUNT

Application

Idle RPM

⁽¹⁾ IAC Counts

Auto. Trans. ⁽²⁾

675

5-30

Man. Trans. ⁽³⁾

800

5-30

⁽¹⁾	Add 2 counts for engines with less than 500 miles. On V8 engines, add 2 counts for every 1000 ft. above sea level.

⁽²⁾	Automatic transmission in Drive.

⁽³⁾	Manual transmission in Neutral. Tech 1 scan tester will display "RDL" with transmission in Neutral.