Chrysler Full-Size Trucks 1967-1988 Repair Guide

Fuel Injected Engines

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MINIMUM IDLE SPEED ADJUSTMENT



See Figures 1 and 2

Normal idle speed is controlled by the logic module or SMEC. This adjustment is the minimum idle speed with the Automatic Idle Speed (AIS) closed.

  1. Before adjusting the idle on an electronic fuel injected vehicle, the following items must be checked (and corrected, if necessary) :

    AIS motor operation
     
    Engine vacuum and/or EGR leaks
     
    Engine timing
     
    Coolant temperature sensor operation
     

  2.  
  3. Connect a tachometer and timing light to the engine, according to the manufacturer's instructions.
  4.  
  5. Close the AIS by using ATM tester C-4805 or equivalent, and ATM test code #03.
  6.  
  7. Connect a jumper to the radiator fan, so that it will run continuously.
  8.  
  9. Start and run the engine for 3 minutes to allow the idle speed to stabilize.
  10.  
  11. Check engine rpm and compare the result with the specifications listed on the underhood emission control sticker.
  12.  
  13. If idle rpm is not within specifications, use tool C-4804 or equivalent to turn the idle speed adjusting screw to obtain 790-810 rpm. If the underhood emission sticker specifications are different, use those values for adjustment.
  14.  

If idle will not adjust down check for binding linkage, speed control servo cable adjustment or throttle shaft binding.

  1. Turn the engine OFF , then disconnect the tachometer, reattach the AIS wire, and remove the jumper wire from the fan motor.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Throttle body-V6 engine



Click image to see an enlarged view

Fig. Fig. 2: Throttle body-V8 engine

 
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