Symptoms - Sensors/Systems

WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.

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) 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. Refer to Emission Hose Routing Diagram . 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 the Electronic Ignition (EI) System Description .
Hesitation, Sag, Stumble	Inspect the accelerator pedal position (APP) sensor and the related wiring. Refer to Throttle Actuator Control (TAC) System Description . 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 .