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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Canyon Pickup - 2WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 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 in Symptoms - Engine Controls .
    • 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

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

    • 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 .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • 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:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - 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 .
       - MAP sensor operation--Refer to Altitude Versus Barometric Pressure .
       - 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:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage .
       - Vacuum leaks
       - Proper MAP sensor operation
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Diagnosis .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - 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:

    •  Spark Plug Inspection
    • 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 .