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

Surges/Chuggles

Inspection/Test	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.
Preliminary	Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information. Search for bulletins. Ensure that the driver understands the transmission torque converter clutch (TCC), and A/C compressor operation as explained in the owners manual. Inform the customer how the TCC and the A/C clutch operates.
Sensor/System	Monitor the heated oxygen sensors (HO2S). The heated oxygen sensors should respond quickly to different throttle positions. If not, inspect the HO2S for silicon or other contaminants from fuel or use of improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage, which is a rich exhaust indication. Refer to Silicon Contamination of Heated Oxygen Sensors Notice. The powertrain control module (PCM) will reduce the amount of fuel delivered to the engine, causing a severe driveability condition. Inspect mass air filter (MAF) sensor and related wiring. Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body. Monitor the 24X crank sensor and the CMP sensor signal present parameters on the scan tool. If both sensors are not responding, test each sensor feed circuit. Each sensor uses a separate supply circuit but are internally connected to power within the PCM. Test all CKP sensor A and CMP sensor circuits for intermittents. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Monitor the 3X crank sensor parameter on the scan tool. If the 3X crank sensor parameter is not responding, inspect the CKP sensor B and related circuits for intermittents. Inspect the ignition control (IC) circuit, IC timing control circuit, low resolution engine speed signal circuit and the low reference circuit for intermittents. If these circuits become open or shorted, they may not set a DTC immediately but are capable of causing driveability complaints. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Test the CKP sensor B for an internal short. Refer to Electronic Ignition (EI) System Diagnosis . Test the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
Fuel System	Test the fuel pressure. Refer to Fuel System Diagnosis . Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (With Special Tool) . Ensure that each fuel injector harness is connected to the correct fuel injector/cylinder. Inspect any items which may cause an engine to run rich, long term fuel trim is significantly in the negative range. Refer to Diagnostic Aids for DTC P0172. Inspect any items that may cause an engine to run lean, long term fuel trim is significantly in the positive range. Refer to Diagnostic Aids for DTC P0171.
Ignition System	Inspect for proper ignition voltage output using the following steps: Attach the J 26792 Spark Tester to engine ground. See Special Tools . Connect the spark plug end of the spark plug wire to the J 26792 . See Special Tools . Connect the other end of the spark plug wire to the coil being tested. Connect the spark plug end of the companion spark plug wire to ground. The companion spark plug wire is the wire attached to the corresponding coil tower. Crank the engine while observing the J 26792 . See Special Tools . A spark should be observed. Repeat the above steps for each coil. If spark is not present at the coils, inspect for the following conditions: Coils-Cracks, carbon tracking/arcing, or a resistance value outside the specified range. Coil Resistance: 5000-8000Ω (5K-8KΩ) Spark Plug wires-signs of arcing, cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range. Spark Plug Wire Resistance: 9868Ω per meter (3000Ω per foot) IMPORTANT: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. Ignition voltage will arc to ground when a secondary component is faulty. Defective ignition module Ignition system wiring-Loose ignition module voltage supply or ground connection, or damaged system wiring. Remove spark plugs and inspect for the following conditions: Fouled plugs Cracks Wear Improper gap Burned or damaged electrodes Improper heat range or reach If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Inspection .
Additional	Test the TCC operation. Inspect the exhaust system for possible restriction: Inspect the exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or possible internal failure. Test for possible catalytic converter restrictions by testing the exhaust system back pressure.