GM Firebird 1982-1992 Repair Guide

Idle Speed

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2-BBL CARBURETOR



Without Air Conditioning

See Figure 1

The engine must be running in "Closed Loop'' mode (engine fully warmed) when making all idle speed adjustments. In this mode, the oxygen sensor affects control of the fuel delivery.

  1. Refer to the emission label on the vehicle and prepare the engine for adjustments (set the timing). Remove the air cleaner and set the parking brake. Connect a tachometer to the distributor connector.
  2.  
  3. Place the transmission in DRIVE for automatic transmission, or NEUTRAL for manual transmission; make sure that the solenoid is energized.
  4.  
  5. Open the throttle slightly to allow the solenoid plunger to extend. Adjust the curb idle speed to the specified rpm by turning the solenoid screw.
  6.  
  7. De-energize the solenoid by disconnecting the electrical lead.
  8.  
  9. Set the basic idle speed rpm by turning the idle speed screw. After adjustment, reconnect the solenoid electrical lead.
  10.  
  11. Remove the tachometer and install the air cleaner.
  12.  



Click image to see an enlarged view

Fig. Fig. 1: Idle speed adjustments-2-bbl carburetor (without air conditioning)

With Air Conditioning

See Figure 2

The engine must be running in "Closed Loop'' mode (engine fully warmed) when making all idle speed adjustments. In this mode, the oxygen sensor affects control of the fuel delivery.

  1. Refer to the emission label on the vehicle and prepare the engine for adjustments (set the timing). Remove the air cleaner and set the parking brake. Connect a tachometer to the distributor connector.
  2.  
  3. Place the transmission in DRIVE for automatic transmission, or NEUTRAL for manual transmission. Turn the air conditioning OFF and set the curb idle speed by turning the idle speed screw.
  4.  
  5. Disconnect the electrical lead at the A/C compressor, then turn the A/C switch ON .
  6.  
  7. With the solenoid energized, open the throttle slightly to allow the solenoid plunger to extend.
  8.  
  9. Turn the solenoid screw to adjust to the specified rpm. After adjustment, reconnect the A/C compressor lead and turn the air conditioning OFF .
  10.  
  11. Remove the tachometer and install the air cleaner.
  12.  



Click image to see an enlarged view

Fig. Fig. 2: Idle speed adjustments-2-bbl carburetor (with air conditioning)

4-BBL CARBURETOR



Without Air Conditioning

See Figure 3

The engine must be running in "Closed Loop'' mode (engine fully warmed) when making all idle speed adjustments. In this mode, the oxygen sensor affects control of the fuel delivery.

  1. Refer to the emission label on the vehicle and prepare the engine for adjustments (set the timing). Set the parking brake. Connect a tachometer to the distributor connector.
  2.  
  3. Place the transmission in DRIVE for automatic transmission, or NEUTRAL for manual transmission.
  4.  
  5. De-energize the idle speed solenoid by disconnecting the electrical lead.
  6.  
  7. Set the basic idle speed rpm by turning the idle speed screw.
  8.  
  9. Connect a jumper wire from a 12-volt power supply to the solenoid.
  10.  
  11. Open the throttle partially to ensure that the solenoid plunger is fully extended, and allow the throttle lever to close on the plunger.
  12.  
  13. Turn the solenoid plunger to adjust to the specified rpm. After adjustment, disconnect the jumper wire and reconnect the solenoid electrical lead.
  14.  
  15. Remove the tachometer and install the air cleaner.
  16.  



Click image to see an enlarged view

Fig. Fig. 3: Idle speed adjustments-4-bbl carburetor

With Air Conditioning

See Figure 3

The engine must be running in "Closed Loop'' mode (engine fully warmed) when making all idle speed adjustments. In this mode, the oxygen sensor affects control of the fuel delivery.

  1. Refer to the emission label on the vehicle and prepare the engine for adjustments (set the timing). Set the parking brake. Connect a tachometer to the distributor connector.
  2.  
  3. Place the transmission in DRIVE for automatic transmission, or NEUTRAL for manual transmission. Turn the air conditioning OFF .
  4.  
  5. De-energize the idle speed solenoid by disconnecting the electrical lead.
  6.  
  7. Set the basic idle speed rpm by turning the idle speed screw. After adjustment, reconnect the solenoid electrical lead.
  8.  
  9. Disconnect the electrical lead from the A/C compressor and turn the A/C switch ON .
  10.  
  11. Open the throttle partially to ensure that the solenoid plunger is fully extended, and allow the throttle lever to close on the plunger.
  12.  
  13. Turn the solenoid plunger to adjust to the specified rpm. After adjustment, reconnect the A/C compressor lead and turn the air conditioning OFF .
  14.  
  15. Remove the tachometer and install the air cleaner.
  16.  

 
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