Chart 13 Improper Idle Speed

Check memory for codes. Diagnose and repair as required.

Perform switch tests. Diagnose and repair as required.

ROUGH IDLE
- Check EGR operation
- Check compressor signal
- Check for vacuum leaks
- Check ignition timing
- Low fuel pressure

IDLE SPEED TOO LOW (BELOW 500 RPM)
- Check TPS adjustment
- Check ISC actuator
- Check for running on one injector
- Check fuel system, see chart #4
- Enter diagnostic series .9.6 and check for movement of the ISC Motor.
^ Motor does not move or only in one direction:
- Treat problem as a hard code 30, start at chart at "4"
^ ISC Motor moves in both directions:
- Problem is not DFI

IDLE SPEED TOO HIGH (ABOVE 600 RPM)
- Check ignition timing
- Check TPS adjustment
- Check for vacuum leaks
- Enter diagnostic series .9.6 and check for movement of the ISC Motor.
^ Motor does not move or only in one direction:
- Treat problem as a hard code 30, start at chart at "4"
^ ISC Motor moves in both directions:
- Problem is not DFI


AFTER ABOVE CHECKS FAIL TO CORRECT THE PROBLEM:
Temporarily install new ECM. If this does not cure the problem, problem is not with the DFI system.