For 1990-2009 cars

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:

• | Ignition System Specifications

• | Spark Plug Replacement

• | 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 .