Minimum Idle Speed

On-Board Diagnostics Diagram - Part 1 Of 2:

On-Board Diagnostics Diagram - Part 2 Of 2:

NOTE: This adjustment should ONLY be performed when the throttle body has been replaced or when required to do so by diagnostic procedures. Engine should be at normal operating temperature before making any adjustment.


If the engine idle speed is not within the above limits (too high), check for vacuum leaks at the throttle body, intake manifold, vacuum fittings, tees and hoses. If the minimum air setting is made with a vacuum leak present, fuel control can be adversely affected throughout all driving ranges.


The minimum idle speed screw, used to regulate the minimum idle speed of the engine is pre-adjusted at the factory. If it is necessary to adjust the minimum idle speed screw, use tool J-38457 or equivalent.



REMOVING IDLE STOP SCREW PLUG

The minimum idle speed screw, used to regulate the minimum idle speed of the engine is pre-adjusted at the factory. If it is necessary to adjust the minimum idle speed screw, pierce the plug with an awl and apply leverage to remove it. The plug can be discarded and need not be replaced.


MINIMUM AIR ADJUSTMENT

1. Visually check all vacuum hoses for splits, leaks or cuts. Repair as needed.

2. Start the engine. Operate the engine until coolant temperature is greater than 80°C.

3. Disable the generator by grounding the green harness connector plug adjacent to the generator.

4. Check ignition timing.

5. Enter diagnostics and select PCM override PS03 (ISC Motor).

6. Press the "COOLER" button on the CCP to retract the ISC motor. This action will disengage the A/C compressor and command the generator "OFF". The ISC motor will retract slowly to a fully retracted position (about 20 seconds). Verify that the throttle lever is resting on the minimum idle speed screw. With the ISC plunger fully retracted, disconnect the ISC harness. If the engine stalled at minimum air (ISC retracted), check the throttle blades for deposits that might restrict air flow. If there are deposits, clean the throttle bores and the area behind and around the throttle plates.

7. With the ISC fully retracted, the plunger should not be touching the throttle lever. If contact is noted, adjust the ISC plunger (turn in) with pliers so that it is not touching the throttle lever. The throttle lever must be resting on the minimum air screw. Make sure that the throttle is not being bound by the throttle, cruise, or TV cables.

8. Check the minimum idle speed using PCM data parameter PD11. Use an average reading of rpm to check minimum idle rpm.
^ For vehicles with 0-500 odometer miles:
Minimum idle rpm should be 450-500 rpm.
^ For vehicles with more that 500 odometer miles:
Minimum idle rpm should be 500-550 rpm.

9. If the minimum idle speed is out of limits, adjust the minimum idle screw to obtain the following idle speed
^ For vehicles with 0-500 odometer miles:
Set Minimum idle rpm to 475 rpm.
^ For vehicles with more that 500 odometer miles:
Set Minimum idle rpm to 525 rpm.

NOTE: If the idle speed cannot be corrected, check that the throttle is not held off the minimum idle speed screw because of linkage or cable binding. Also, check for leaking vacuum hoses or air leaks at the throttle body or intake manifold.

10. Reconnect the ISC motor harness. Remove the generator disable ground wire. If minimum idle speed was adjusted, adjust the TP.