GM Service Manual Online
For 1990-2009 cars only

Sensor/System

Symptoms

Sensor/System

Find the symptom in the left column and perform the test/inspection procedure in the right column, be sure to review each cell of the table to identify all tests for a symptom.

    â€¢ Hard Start
    â€¢ Surges/Chuggles
    â€¢ Hesitation, Sag, Stumble
    â€¢ Cuts Out, Misses
    â€¢ Poor Fuel Economy
    â€¢ Rough, Unstable, or Incorrect Idle and Stalling
    â€¢ Backfire
    â€¢ Inspect the mass air flow (MAF) sensor for proper installation, obstruction, contamination, and damage. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .
    â€¢ Inspect the MAF sensor for proper seating of the connector and terminals.
    â€¢ Inspect the manifold absolute pressure (MAP) sensor for proper installation, obstruction, and damage. Refer to Manifold Absolute Pressure Sensor Replacement .
    â€¢ Ensure the quality of the MAP sensor vacuum source.
    â€¢ Hard Start
    â€¢ Detonation/Spark Knock
    â€¢ Hesitation, Sag, Stumble
    â€¢ Poor Fuel Economy
    â€¢ Rough, Unstable, or Incorrect Idle and Stalling
    â€¢ Inspect for vacuum leaks and other unmetered air.
    â€¢ Test the engine coolant temperature (ECT) sensor for being shifted in value. Refer to the Temperature Versus Resistance - Engine Coolant Temperature Sensor .
    â€¢ Surges/Chuggles
    â€¢ Lack of Power, Sluggishness, or Sponginess
    â€¢ Detonation/Spark Knock
    â€¢ Poor Fuel Economy
    â€¢ Backfire

Monitor the Knock Sensor (KS) System for excessive spark retard activity. Refer to the Knock Sensor description within in the Electronic Ignition (EI) System Description .

Hesitation, Sag, Stumble

Inspect the accelerator pedal position (APP) sensor and the related wiring.

Inspect the Throttle Actuator Control (TAC) System for proper operation.

    â€¢ Surges/Chuggles
    â€¢ Lack of Power, Sluggishness, or Sponginess
    â€¢ Hesitation, Sag, Stumble
    â€¢ Cuts Out, Misses
    â€¢ Poor Fuel Economy
    â€¢ Rough, Unstable, or Incorrect Idle and Stalling
    â€¢ Backfire

Inspect for contaminated oxygen sensor (O2S).

Poor Fuel Economy

    â€¢ Inspect for proper tire inflation.
    â€¢ Inspect for a dirty or restricted air filter.
    â€¢ Fuel quality
    â€¢ Acceleration rate too much or too often
    â€¢ Inspect for incorrect operation of the speedometer.
    â€¢ Hard Start
    â€¢ Surges/Chuggles
    â€¢ Poor Fuel Economy
    â€¢ Rough, Unstable, or Incorrect Idle and Stalling
    â€¢ Backfire
    â€¢ Inspect the camshaft actuator for correct operation. Refer to Camshaft Actuator System Description .
    â€¢ Inspect the intake manifold tuning valve for correct operation. Refer to Intake Manifold Tuning Valve System Description