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Home >> Geo >> 1991 >> Metro Base, 2D Hatchback, Automatic >> Repair and Diagnosis >> Engine Performance >> Engine Controls - Adjustments >> Idle Speed & Mixture >> Idle Speed

Idle Speed

  1. Place transaxle in Park (A/T) or Neutral (M/T) and apply parking brake. Ensure throttle cable has at least .12-.20" (3.1-5.1 mm) of slack in the cable. Adjust throttle cable slack (if necessary).
  2. Ensure all emission hoses and air cleaner are properly installed. Install tachometer. Ensure all accessories are off. Start engine and warm to normal operating temperature.
  3. Install spare fuse in diagnostic switch terminal in fuse box. See Fig 1 . Idle speed should be within specification. See IDLE SPEED SPECIFICATIONS table.
    Fig 1: Adjusting Idle Speed
    G121580Courtesy of GENERAL MOTORS CORP.
  4. If idle speed requires adjustment, remove idle speed adjusting screw cap from throttle body, just above throttle lever. Turn idle speed adjusting screw inward to increase idle speed or outward to decrease idle speed. See Fig 1 .
  5. On A/C equipped models, turn A/C on low speed. With A/C operating, idle speed should be within specification. See A/C IDLE SPEED SPECIFICATIONS table.
  6. If idle speed requires adjustment, rotate adjustment screw on air conditioner Vacuum Switching Valve (VSV) to obtain correct idle speed. See Fig 1 . Air conditioner VSV is mounted on firewall, to the right of ignition coil.
  7. On all models, turn engine off. Remove spare fuse from diagnostic switch terminal in fuse box. Install idle speed adjusting screw cap (if removed) and remove tachometer.
IDLE SPEED SPECIFICATIONS (1)

Application Idle RPM
Metro & Metro LSi
A/T (2)(3) 850
M/T (2)(3) 800
Convertible (2)(3) 850
Metro XFi (2)(3) 750
(1) If specification differs from emission label, use specification listed on emission label.
(2) Specification listed are with transmission in Neutral on M/T models or in Park on A/T models
(3) Specification listed with fuse installed in diagnostic switch terminal in fuse box.
A/C IDLE SPEED SPECIFICATIONS

Application (1) Engine RPM
Metro (2)
A/T 800-900
M/T 850-950
(1) Specification listed are with transmission in Neutral on M/T models or in Park on A/T models.
(2) Vacuum Switching Valve (VSV) is used for maintaining idle speed during A/C operation.
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