GM Metro/Sprint 1985-1993 Repair Guide

Idle Speed

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ADJUSTMENT



See Figures 1 through 5



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Fig. Fig. 1: Idle speed adjusting screw - carburetor



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Fig. Fig. 2: Idle speed adjusting screw - fuel injection



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Fig. Fig. 3: Air conditioning vacuum solenoid valve adjusting screw - fuel injection



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Fig. Fig. 4: Diagnostic switch connector location - fuel injection



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Fig. Fig. 5: Checking accelerator cable play

1985-88 Carbureted Vehicles

The cooling fan runs and stops automatically according to the coolant temperature. For this reason, make sure that the cooling fan is not running before performing idle speed check and adjustment.

  1. Confirm the following prior to checking or adjusting the idle speed.
    1. Check that the lead wires and hoses of the engine emission control system are connected correctly.
    2.  
    3. Check that the accelerator cable has 0.12-0.20 in. (3-5 mm) free-play when engine is at operating temperature.
    4.  
    5. Check that the ignition timing is within specification.
    6.  
    7. Check that the valve lash is adjusted to specification.
    8.  

  2.  
  3. Connect a tachometer to the engine according to the manufacturer's instructions.
  4.  
  5. Place transaxle gear shift lever in N position and set parking brake.
  6.  
  7. Start engine and warm engine to normal operating temperature.
  8.  
  9. Ensure that the lights, heater fan, rear defogger, cooling fan and air conditioner are OFF .
  10.  
  11. Check the idle speed. If not within specifications, adjust by turning the idle adjusting screw on the carburetor.
  12.  
  13. If idle speed can not be adjusted to specification by turning the adjusting screw, it can be due to a faulty return of the throttle valve or some other mechanical reason. Determine the cause and repair.
  14.  
  15. After idle adjustment, check idle-up system for proper operation.
  16.  
  17. Stop engine and check to ensure that accelerator cable has some play. If not, adjust cable.
  18.  

1987-93 Fuel Injected Vehicles
  1. Confirm the following prior to checking or adjusting the idle speed.
    1. Check that the lead wires and hoses of the engine emission control system are connected correctly.
    2.  
    3. Check that the accelerator cable has 0.12-0.20 in. (3-5 mm) free-play when engine is at operating temperature.
    4.  
    5. Check that the ignition timing is within specification.
    6.  

  2.  
  3. Place automatic transaxle gear shift lever in P position or manual transaxle gear shift lever in NEUTRAL position and set parking brake.
  4.  
  5. Ensure that the lights, heater fan, rear defogger, cooling fan and air conditioner are OFF .
  6.  
  7. Ensure that air cleaner is installed correctly.
  8.  
  9. Connect a tachometer according to the manufacturer's instructions.
  10.  
  11. Remove cover on idle speed adjusting screw.
  12.  
  13. Start engine and warm engine to normal operating temperature.
  14.  
  15. Install a spare fuse into the DIAG SW connector in the fuse block under the left side of the dash.
  16.  
  17. Check and adjust idle speed to specification. Turn idle speed screw in to decrease idle and out to increase idle.
  18.  
  19. If equipped with air conditioning, check and adjust the air conditioner idle speed vacuum solenoid valve.
  20.  
  21. With idle speed correct, turn air conditioner ON .
  22.  
  23. Check that engine idle is within specification or slightly higher. If not, adjust air conditioner vacuum solenoid valve adjusting screw to obtain correct idle.
  24.  
  25. Turn air conditioner OFF and check that idle speed is within specifications.
  26.  

On some vehicles, a slightly higher idle setting on the vacuum solenoid valve may be needed to maintain proper idle characteristics with the air conditioning system operating.

  1. After adjusting idle speed remove the spare fuse from the connector.
  2.  

 
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