Chrysler Full-Size Vans 1967-1988 Repair Guide

Minimum Idle Speed Adjustment


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Adjusting the idle speed control actuator for minimum idle speed

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

  1. Before adjusting the idle on an electronic fuel injected vehicle the following items must be checked.
    1. AIS motor has been checked for operation.
    3. Engine has been checked for vacuum or EGR leaks.
    5. Engine timing has been checked and set to specifications.
    7. Coolant temperature sensor has been checked for operation.

  3. Connect a tachometer and timing light to engine.
  5. Close AIS by using ATM tester C-4805 or equivalent, ATM test code #03.
  7. Connect a jumper to radiator fan so that it will run continuously.
  9. Start and run the engine for 3 minutes to allow the idle speed to stabilize.
  11. Check engine rpm and compare the result with the specifications listed on the underhood emission control sticker.
  13. If idle rpm is not within specifications, use tool C-4804 or equivalent to turn the idle speed adjusting screw to obtain 800 +- 10 rpm. If the underhood emission sticker specifications are different, use those values for adjustment.

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

  1. Turn off the engine, disconnect tachometer, reinstall AIS wire and remove jumper wire from fan motor.

The fuel injection system is under a constant pressure of approximately 14.5 psi. Before servicing any part of the fuel injection system, the system pressure must be released. Use a clean shop towel to catch any fuel spray and take precautions to avoid the risk of fire.