Isuzu Cars and Trucks 1981-1991

Gasoline Fuel Injection Systems

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Idle Speed adjustment
All 4-Cyl. Engines, Except 4XE1 Impulse
  1. Firmly set the parking brake and block the drive wheels.
  2.  
  3. Place the transmission in N .
  4.  
  5. Set the engine tachometer.
  6.  
  7. Make sure the throttle valve is fully closed.
  8.  
  9. If equipped with air conditioning, make sure it is turned OFF .
  10.  
  11. Place the manual transmission in N or the automatic transmission in P .
  12.  
  13. Disconnect the electrical connector from the Vacuum Switching Valve (VSV) on the pressure regulator; the idle speed should be 850 and 19950 rpm.
  14.  
  15. If the idle speed is not correct, turn the adjusting screw A on the throttle body.
  16.  



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Fig. Before checking the idle speed, disconnect the VSV pressure regulator EFI 4ZD1 and 4ZE1 engines



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Fig. Idle adjustment screw EFI 4ZD1 and 4ZE1 engines

4XE1 and V6 Engines
  1. The idle speed is controlled by the ECM and Idle Air Control (IAC) valve. No adjustment is necessary or possible.
  2.  

dash pot touch rotation speed
  1. This system is used on the 1983 and 1988 EFI Impulse with automatic transmission.
  2.  
  3. Push the accelerator pedal fully to the floor. Allow the engine speed to increase and then release the pedal.
  4.  
  5. Check to make sure the engine speed returns to 1,00 and 192,100 rpm and them continues to slowly drop towards the correct idling speed.
  6.  
  7. If not, set the engine speed to 2,000 rpm with the throttle lever.
  8.  
  9. Tighten the adjusting screw until it just makes contact with the dash pot shaft head.
  10.  
  11. Lock the adjusting screw in position with the locknut.
  12.  
  13. Repeat the dash pot touch rotation speed check procedure as described above.
  14.  



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Fig. Dash pot adjustment all EFI engines except 4XE1

Idle mixture adjustment

No idle mixture adjustment is necessary or possible.

 
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