Symptoms - Sensors/Systems

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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.
Hard Start Surges /Chuggles Hesitation, Sag, Stumble Cuts Out, Misses Poor Fuel Economy Rough, Unstable, or Incorrect Idle and Stalling Backfire	Inspect the mass air flow (MAF) sensor for proper installation, obstruction, contamination, and damage. Refer to Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement . Inspect the MAF sensor for proper seating of the connector and terminals. Inspect the manifold absolute pressure (MAP) sensor for proper installation, obstruction, and damage. Refer to Manifold Absolute Pressure (MAP) Sensor Replacement . Ensure the quality of the MAP sensor vacuum source.
Hard Start Detonation/Spark Knock Hesitation, Sag, Stumble Poor Fuel Economy Rough, Unstable, or Incorrect Idle and Stalling	Inspect for vacuum leaks and other unmetered air. Test the engine coolant temperature (ECT) sensor for being shifted in value. Refer to the Temperature vs Resistance .
Surges /Chuggles Lack of Power, Sluggishness, or Sponginess Detonation/Spark Knock Poor Fuel Economy 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.
Surges /Chuggles Lack of Power, Sluggishness, or Sponginess Hesitation, Sag, Stumble Cuts Out, Misses Poor Fuel Economy Rough, Unstable, or Incorrect Idle and Stalling Backfire	Inspect for contaminated oxygen sensor (O2S).
Poor Fuel Economy	Inspect for proper operation of the speedometer. Refer to Speedometer and/or Odometer Inaccurate or Inoperative .
Hard Start Surges /Chuggles Poor Fuel Economy Rough, Unstable, or Incorrect Idle and Stalling Backfire	Inspect the camshaft actuator for correct operation. Refer to Camshaft Actuator System Description .