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 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 and Engine Controls Schematics .

Sensor/System | Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

• | 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.

- | Any water intrusion in the heated oxygen sensor (HO2S) connector

- | The engine oil contaminated by fuel

- | An evaporative emission (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:

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

- | Any water intrusion in the HO2S connector

- | An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage .

- | Any vacuum leaks

- | Incorrect fuel pressure--Refer to Fuel System Diagnosis .

- | Any restricted fuel injectors--Refer to Fuel Injector Diagnosis .

- | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

- | 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 Versus Resistance .

• | Inspect for a skewed 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 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 . 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 .

• | Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust .