GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

Checks

Action

DEFINITION: The 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.
    • Verify that the engine control module (ECM) grounds are clean, tight, and in the correct locations.
    • Remove the air filter element and inspect for restrictions. Refer to Air Cleaner Element Replacement and replace if necessary.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Test or inspect items that can cause an engine to run lean. For a lean condition, refer to DTC P0171 or P0174 .
    • Test or inspect items that can cause an engine to run rich. For a rich condition, refer to DTC P0172 or P0175 .

Sensor/System
    • Test for the correct operation of the intake manifold tuning valve (IMTV) system.
    • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description and DTC P0329 or DTC P0334 .

Ignition System
    • Wet down the secondary ignition system with water from a spray bottle. Wetting the secondary ignition system may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as water is applied.
    • Test the ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis .
    • Remove the spark plugs and inspect for the following conditions:
       - Incorrect heat range
       - Wet plugs
       - Cracks
       - Excessive wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Refer to the following procedures:
    • An incorrect spark plug gap will cause a driveability concern. Refer to Ignition System Specifications .
    • If the spark plugs are fouled by gas, coolant, or oil, determine the cause before replacing the plugs. Refer to the following procedures:
       - For diagnosis of a rich condition, refer to DTC P0172 or P0175 .
       - For diagnosis of coolant or oil fouled spark plugs, refer to Loss of Coolant in Engine Cooling or Symptoms - Engine Mechanical in Engine Mechanical - 2.5L (LBK).
    • Test the crankshaft position (CKP) sensor for the correct resistance. The CKP sensor resistance may be out of range after a hot soak. The resistance should be between 460-620 ohms.
    • Inspect for the correct installation of the ignition coil seals. Incorrect installation may allow water to enter the spark plug area. Inspect for moisture and corrosion.
    • Inspect the ignition coils and the spark plug boots for cracks or carbon tracking.

Engine Mechanical
    • Inspect for excessive oil in the combustion chamber and for leaking valve seals.
    • Test for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical - 2.5L (LBK).
    • Inspect the combustion chambers for excessive carbon buildup. Clean the chambers with top engine cleaner. Follow the instructions on the can.
    • Inspect the following for incorrect basic engine parts:
       - The camshaft
       - The cylinder heads
       - The pistons, connecting rods, and bearings

Additional Inspections
    • Inspect the following exhaust system components:
       - The exhaust system for physical damage.
       - The mufflers for heat distress or possible internal failure.
       - The three-way catalytic converter(s) for restrictions.
       - For more information, refer to Restricted Exhaust in Engine Exhaust.
    • Test the transmission torque converter clutch (TCC). Refer to Diagnostic System Check - Automatic Transmission in Automatic Transmission - ZF 4HP 16.