GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Sunfire 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Lack of Power, Sluggishness, or Sponginess

Inspection/Tests

Action

DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
    • Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement and replace as necessary.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .

Sensor/System
    • Inspect for the following that may cause the engine to run rich:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Any water intrusion in the HO2S connector
       - The engine oil contaminated by fuel
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - A leaking fuel pressure regulator--Refer to Fuel System Diagnosis .
       - A leaking fuel injectors--Refer to Fuel System Diagnosis .
       - Any vacuum hoses that are split, kinked, or improperly connected
       - An air intake duct that is collapsed or restricted--Refer to Air Cleaner Outlet Resonator Replacement .
       - An air filter that is dirty or restricted--Refer to Air Cleaner Element Replacement .
    • Inspect for the following conditions that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Any water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Restricted Exhaust in Engine Exhaust.
       - Any vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Any restricted fuel injectors--Refer to Fuel Injector Balance Test with Tech 2 .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Any vacuum hoses that are split, kinked, or improperly connected
    • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data List .
    • Test the crankshaft position (CKP) sensor for an internal short. Refer to Crankshaft Position Sensor System Diagnosis .

Ignition System
    • In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • Remove spark plugs and inspect for the following conditions:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Verify that the spark plugs are of the correct type.
    • Inspect for proper ignition voltage output with the J 26792 HEI Spark Tester.
    • An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool.
    • Determine the cause of the fouling before replacing the spark plugs.
    • Inspect for damaged or misaligned spark plug boots.
    • Inspect the electronic ignition (EI ) module for proper ground connection.
    • Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .

Engine Mechanical
    • Inspect for incorrect camshaft timing.
    • Inspect for excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • Test for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    • Inspect for incorrect basic engine parts, including the following components:
       - The camshaft--Refer to Camshaft Cleaning and Inspection in Engine Mechanical.
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection in Engine Mechanical.
    • Inspect for excessive crankshaft endplay that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions:
       - A no start
       - A start and stall
       - Erratic Performance

Additional Inspections
    • Inspect the exhaust system for the following possible restrictions:
       - The exhaust system for damaged or collapsed pipes
       - The mufflers for heat distress or internal failure
       - Refer to Restricted Exhaust in Engine Exhaust
    • Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis in Automatic Transaxle 4T40-E/ 4T45-E.