GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Cuts Out, Misses

Checks

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DEFINITION: A steady pulsation or jerking that follows engine speed, which is usually more pronounced as the engine load increases. This condition is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or at low speed.

Preliminary
    • 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 proper 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 down 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 improper 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 the following engine mechanical conditions:
       - Excessive oil in the combustion chamber or leaking valve seals
       - Incorrect cylinder compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Incorrect valve timing
       - Worn rocker arms
       - Broken valve springs
       - Excessive carbon buildup in the combustion chambers. Clean the chambers with top engine cleaner. Follow the instructions on the can.
       - For more information, refer to the following procedures in Engine Mechanical - 2.5L (LBK):
   •  Oil Leak Diagnosis
    • Inspect the following for incorrect basic engine parts:
       - The camshaft
       - The cylinder heads
       - The pistons, connecting rods, and bearings

Additional Checks
    • 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.
    • Electromagnetic interference (EMI) on the reference circuit can cause a misfire condition. You can usually detect EMI with a scan tool by monitoring the engine speed parameter. A sudden increase in the engine speed parameter with little change in actual engine speed indicates that EMI is present. Inspect the high voltage components near the ignition control circuit if a condition exists.