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Engine Performance System Adjustments - 5.0l Chevrolet Chevy Van G2500

Adjustments ~259 words

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All models are equipped with hydraulic lifters. Adjustments are not required.

IGNITION TIMING

Note. Ignition timing is controlled by control module and is not adjustable.

IDLE SPEED & MIXTURE

Note. DO NOT attempt to adjust idle mixture and idle speed. Both are controlled by Powertrain Control Module (PCM). 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 tool. See CONTROLLED IDLE SPEED & IAC COUNT table. Minimum idle speed adjustment can only be performed on the

CONTROLLED IDLE SPEED CHECK

  1. 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 tool to Data Link Connector (DLC). Put scan tool into OPEN mode.
  2. Start engine and bring to normal operating temperature. Check for correct state of transmission range switch on scan tool. Check if idle speed and IAC valve pintle position (counts) are as specified. See CONTROLLED IDLE SPEED & IAC COUNT table.
  3. If idle speed is not within specification, refer to the «TESTS W/O CODES - 5.0L»(/chevrolet/chevy-van-g2500/1996-1998/remont/testing-diagnostics/#engine-controls-tests-wo-codes-50l) article.
ApplicationIdle RPM(1) IAC Counts
Auto. Trans. (2)675-725Varies
Man. Trans. (3)675-725Varies
(1) Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level. (2) Automatic transmission in Drive. (3) Manual transmission in Neutral. Tech 1 scan tool will display "RDL" with transmission in Neutral.
(1)Add 2 counts for engines with less than 500 miles. Add 2 counts for every 1000 ft. above sea level.
(2)Automatic transmission in Drive.
(3)Manual transmission in Neutral. Tech 1 scan tool will display "RDL" with transmission in Neutral.

CONTROLLED IDLE SPEED & IAC COUNT

THROTTLE POSITION (TP) SENSOR

TP sensor output voltage should be .85 volt or less at idle (closed throttle) and is not adjustable.

See also:
• TESTS W/O CODES - 5.0L

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