GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 STS 🢒 Engine 🢒 Engine Controls and Fuel - 3.6L 🢒 Surges/Chuggles

Inspections

Action

DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down without a change in the accelerator pedal position.

Preliminary
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the engine control system grounds for being clean, tight, and in the correct locations. Refer to Engine Controls Schematics . Ensure the resistance between the engine control module (ECM) housing and the battery negative cable is less than 0.5 ohm.
    • Verify that the ECM and ECM bracket fasteners are at the correct torque.
    • Ensure that the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owner manual. Inform the customer how the TCC and the A/C clutch operates.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Verify that each 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 the items that cause an engine to run rich. For a rich condition, refer to DTC P2178 or P2180 and DTC P2188 or P2190 .
    • Test the items that can cause an engine to run lean. For a lean condition, refer to DTC P2177 or P2179 and DTC P2187 or P2189 .

Ignition System
    • 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.
    • Test for proper ignition voltage output with a J 26792 Spark Tester. If you suspect an ignition system condition exists, refer to Electronic Ignition (EI) System Diagnosis .
    • 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 the following procedures:
    • If the spark plugs are gas, coolant or oil fouled, determine the cause before replacing the spark plugs. Refer to the following procedures:
       - Test the items that cause an engine to run rich. For a rich condition, refer to DTC P2178 or P2180 and DTC P2188 or P2190 .
       - For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant .
       - For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis for the 3.6L (LY7) engine.
    • Inspect the crankshaft position (CKP) sensor for the correct resistance. The sensor resistance may be out of range after a hot soak. Measure that the resistance remains within 700-1,200 ohms at all temperatures.
    • Inspect the spark plug boots and terminals for burning or micro-arcing, corrosion, and damage to the insulation.

Additional
    • Inspect the vacuum hoses for splits and kinks. Verify that the connections and routing are as shown on the Vehicle Emission Control Information Label, refer to Emission Hose Routing Diagram .
    • Inspect for a condition with the camshaft actuator system. A camshaft actuator that is stuck in the full advance or retard position may cause this symptom. Refer to DTC P0011, P0014, P0021, or P0024 .
    • Test the TCC operation. A TCC applying too soon can cause the engine to spark knock, surge or chuggle. Refer to Torque Converter Diagnosis .
    • Test the A/C clutch for the correct operation. Refer to Symptoms - HVAC Systems - Automatic .