GM Service Manual Online
For 1990-2009 cars only

Important Preliminary Inspections

Inspections

Action

Before Using This Section

Before using this section, you should have performed the Diagnostic System Check - Engine Controls . Several of the following symptom procedures call for a careful visual and physical inspection. The visual and physical inspections are very important. These inspections can lead to correcting a problem, which may save valuable time.

  1. Verify the customer complaint.
  2. Locate the correct symptom table.
  3. Inspect the items indicated under that symptom.

Visual and Physical

    â€¢ Inspect the powertrain control module (PCM) grounds for being clean, tight, and in their proper location. Refer to Power and Grounding Component Views in Wiring Systems.
    â€¢ Inspect the vacuum hoses for splits, kinks, and improper connections, as shown on the Vehicle Emission Control Information label.
    â€¢ Inspect thoroughly for any type of leak or restriction in the exhaust. Refer to Exhaust Leakage or Restricted Exhaust in Engine Exhaust.
    â€¢ Inspect for vacuum leaks at all the mounting areas of the intake manifold sealing surfaces.
    â€¢ Inspect the spark plug wires. Refer to Spark Plug Wire Inspection .
    â€¢ The following symptom tables contain groups of possible causes for each symptom. In order to determine if a specific vehicle is using a particular system or component, refer to Powertrain Control Module Connector End Views for an application.

Symptom

Use the following tables when diagnosing a symptom complaint.

    â€¢  Intermittent Conditions
    â€¢  Hard Start
    â€¢  Surges/Chuggles
    â€¢  Detonation/Spark Knock
    â€¢  Hesitation, Sag, Stumble
    â€¢  Cuts Out, Misses
    â€¢  Poor Fuel Economy
    â€¢  Dieseling, Run-On
    â€¢  Backfire