GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Surges/Chuggles

Surges/Chuggles

Checks

Action

DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal position.

Preliminary
    • Refer to Important Preliminary Checks 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.
    • Make sure the driver understands the operation of the transmission torque converter clutch (TCC) and the A/C compressor operation as explained in the owner's manual. Inform the customer how the TCC and the A/C clutch operate.

Sensor/System

Test the heated oxygen sensors (HO2S). The HO2S should respond quickly to a change in throttle position. If the HO2S do not respond to different throttle positions, inspect for contamination from fuel, silicon, or the incorrect use of RTV sealant. The sensors may have a white powdery coating and result in a high, but false, signal voltage, which gives a rich exhaust indication. The ECM reduces the amount of fuel delivered to the engine, causing a driveability condition.

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 .
    • Verify that the fuel injector harness is connected to the correct injector/cylinder according to the firing order.
    • 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 .

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 the 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:
       - Incorrect heat range
       - Wet plugs
       - Cracks
       - Excessive wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Refer to the following procedures:
    • 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).
    • 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.

Additional Checks
    • Inspect the vacuum hoses for splits or kinks. Verify that the routing and connections are as shown on the Vehicle Emission Control Information label. Refer to Emission Hose Routing Diagram .
    • Test the transmission torque converter clutch (TCC). A TCC applying too soon can cause the engine to surge or chuggle. Refer to Diagnostic System Check - Automatic Transmission in Automatic Transmission - ZF 4HP 16.
    • Test the A/C clutch. Refer to Symptoms - HVAC Systems - Manual in HVAC Systems - Manual.