Idle Speed & Mixture (Gasoline)

1999 GMC Forward Control 5.7 R, AutomaticSECTION Idle Speed & Mixture (Gasoline)

Idle mixture on fuel injected models is controlled by PCM and is not adjustable. Controlled idle speed and IAC count can be checked using scan tool. See CONTROLLED IDLE SPEED & IAC COUNT table. For controlled idle speed adjustment procedures, see appropriate ON-VEHICLE ADJUSTMENTS article.

CONTROLLED IDLE SPEED & IAC COUNT

Application Idle RPM IAC Counts
1.6L 725-775 (1) 17-30
2.0L (2) (2)
2.2L (2) 5-60
3.4L (2) 10-40
4.3L, 4.8L, 5.3L & 6.0L (2) Varies
5.0L & 5.7L 650 Varies
7.4L 650 60
(1) Specification is duty cycle percentage.
(2) Information is not available from manufacturer.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.