- Important Preliminary Checks

Before using this section you should have performed the "On-Board Diagnostic System Check" and determined that:

1. The ECM and Malfunction Indicator Lamp (MIL) are operating correctly.

2. There are no Diagnostic Trouble Codes (DTCs) stored, or there is a diagnostic code but no MIL.

3. Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed, because they can lead to correcting a problem without further checks and can save valuable time. Testing and Inspection

Before Starting

^ Check the ECM grounds for being clean, tight, and in their proper locations. Refer to Starting and Charging / Power and Ground / Locations.

^ Check the vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information" label. Check thoroughly for any type of leak or restriction.

^ Check for air leaks at all mounting areas of the intake manifold sealing surfaces.

^ Check the ignition wires for the following:

- Cracking

- Hardness

- Proper routing

- Carbon tracking

^ Check the wiring for proper connections, pinches, and cuts. Refer to Diagrams.

^ The following symptom tables contain groups of possible causes for each symptom and cover several engines. These procedures do not have to be done in consecutive order. If the scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a specific vehicle is using a particular system or component, refer to the "ECM Wiring Diagrams" for application.

Symptom

Verify the customer complaint, and locate the correct symptom in the table of contents. Check the items indicated under that symptom.
Intermittents