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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Uplander - 4WD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

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 Beginning 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.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel system. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect for the following conditions that may cause the engine to run rich:
       - Water intrusion in the heated oxygen sensor (HO2S) connector
       - Engine oil contaminated by fuel
       - An evaporative emission (EVAP) canister purge condition
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Leaking fuel injectors--Refer to Fuel System Diagnosis .
       - For proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions and Scan Tool Data List .
       - Blockage on the inlet screen of the MAF sensor
       - Vacuum hoses that are split, kinked, or improperly connected
       - An air intake duct that is collapsed or restricted
       - An air filter that is dirty or restricted.
    • Inspect for the following conditions that may cause the engine to run lean:
       - Water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
       - Vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 .
       - For proper operation of the MAF sensor--Refer to Scan Tool Data Definitions and Scan Tool Data List .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Sensor/System
    • Inspect the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity.

Ignition System
    • Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied . Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. If a misfiring cylinder can be located with a misfire, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
    • Inspect for proper ignition voltage output with the J 26792 Spark Tester.
    • Remove the spark plugs and inspect for the following conditions:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Refer to Spark Plug Inspection .
    • An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement .
    • Determine the cause of the fouling before replacing the spark plugs.
    • Inspect the spark plug wires for signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range. Refer to Ignition System Specifications .
    • Inspect for loose ignition coil grounds.

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 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 and Bearings 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 crankshaft position (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 possible restrictions. Refer to Restricted Exhaust in Engine Exhaust
    • Inspect the exhaust system for damaged or collapsed pipes.
    • Inspect the mufflers for heat distress or internal failure.
    • Inspect the transmission torque converter clutch (TCC) for proper operation.