Section 145 (Engine Control System - 3.6L (Ly7) - Troubleshooting & Diagnosis): Surges/Chuggles

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

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 Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Ensure the resistance between the engine control module (ECM) housing and the battery negative cable is less than 0.5 ohms. 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's 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 (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . 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 Coil Test . Test the items that cause an engine to run rich. For a rich condition, refer to DTC P2178 or DTC P2188 . Test the items that can cause an engine to run lean. For a lean condition, refer to DTC P2177 or DTC P2187 .
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. See Special Tools . 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: Spark Plug Replacement Ignition System Specifications Spark Plug Inspection If the spark plugs are gas, coolant or oil fouled, determine the cause before replacing the spark plugs. Refer to the following procedures: For diagnosis of a rich condition, refer to DTC P2178 or DTC P2188 . For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant in Engine Cooling. For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical - 3.6L (LY7). 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 . Test the transmission TCC operation. A TCC applying too soon can cause the engine to spark knock, surge or chuggle. Refer to Torque Converter Diagnosis Procedure in Automatic Transaxle - 4T65-E. Test the A/C clutch for the correct operation. Refer to Symptoms - HVAC Systems - Automatic in HVAC Systems - Automatic.