Section 86 (Engine Control System & Fuel System - 3.7L - Diagnosis & Troubleshooting): Surges/Chuggles

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Surges/Chuggles

Inspection/Tests	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 Inspections Before Beginning . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics . Verify the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owners manual.
Sensor/System	NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice . Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature Versus Resistance . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Altitude Versus Barometric Pressure .
Fuel System	Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Diagnosis (w/CH47976) or Fuel Injector Diagnosis (w/J39021 or w/Tech 2) . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) . Verify that each fuel injector harness is connected to the correct fuel injector or cylinder. Relocate the fuel injector harnesses as necessary. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the heated oxygen sensor (HO2S) connector Purging of a saturated evaporative emission (EVAP) canister Incorrect fuel pressure-Refer to Fuel System Diagnosis . A leaking fuel pressure regulator-Refer to Fuel System Diagnosis . Leaking fuel injectors-Refer to Fuel System Diagnosis . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted-Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice . Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage . Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Restricted fuel injectors-Refer to Fuel Injector Diagnosis (w/CH47976) or Fuel Injector Diagnosis (w/J39021 or w/Tech 2) . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) . Vacuum hoses that are split, kinked, or improperly connected
Ignition System	In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement . Inspect for proper secondary ignition voltage output with the J 26792 HEI Spark Tester. An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs. Inspect for damaged or misaligned spark plug boots. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the symptom occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
Additional Inspections	Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) for proper operation. Refer to Symptoms - Automatic Transmission . Test the A/C clutch for proper operation. Refer to Symptoms - HVAC Systems - Manual . Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust .