Engine Controls (Troubleshooting & Diagnosis): Troubleshooting: Surges/Chuggles

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 Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
Sensor/System	NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect for the following that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Any water intrusion in the heated oxygen sensor (HO2S) connector The engine oil contaminated by fuel An EVAP canister purge condition Incorrect fuel pressure-Refer to Fuel System Diagnosis . Any leaking fuel injectors-Refer to Fuel System Diagnosis . Any 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 in Cautions and Notices. Any water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine-Refer to Exhaust Leakage in Engine Exhaust. Any vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Any restricted fuel injectors-Refer to Fuel Injector Coil Test . Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Any vacuum hoses that are split, kinked, or improperly connected Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . Inspect for a skewed manifold absolute pressure (MAP) sensor. Refer to Altitude vs Barometric Pressure .
Fuel System	Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Coil Test . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary.
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 Remove spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Verify that the spark plugs are of the correct type. Inspect for proper ignition system output. Refer to Electronic Ignition (EI) System Diagnosis . An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool. Determine the cause of the fouling before replacing the spark plugs. Inspect for damaged or misaligned spark plug boots. Inspect the electronic ignition (EI) module for proper ground connection. 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 .
Engine Mechanical	Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Camshaft Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance
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. Test the A/C clutch for proper operation. Refer to Symptoms - HVAC Systems - Manual in HVAC Systems-Manual. Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust.