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DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. This condition is not normally felt above 1,500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed.

Preliminary
    • Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls .
    • Search for bulletins.
    • Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics .
    • Remove the air filter element and inspect for dirt and for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System 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 .
    • Inspect for the following conditions 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 .
       - Proper operation of the manifold absolute pressure (MAP) sensor--Refer to DTC P0106 .
       - 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
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Balance Test with Tech 2 .
       - Proper operation of the MAP sensor--Refer to DTC P0106 .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Sensor/System
    • Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature Versus Resistance .
    • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data List .
    • Inspect for throttle body tampering, excessive deposits, or damage.
    • Inspect for a vacuum leak.
    • Inspect the crankcase ventilation system for proper operation. Refer to Crankcase Ventilation System Inspection/Diagnosis .

Ignition System
    • In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • Inspect for proper secondary ignition voltage output with J 26792 HEI Spark Tester.
    • Inspect the distributor cap and rotor. Refer to Distributor Inspection .
    • 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 spark plug wires. Refer to Spark Plug Wire Inspection .
    • 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 .
    • Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water.

Engine Mechanical
    • Inspect engine mechanical for the following:
       - Compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Worn rocker arms
       - Broken valve springs
       - Excessive oil in combustion chamber or leaking valve seals.
       - For more information, refer to one or more of the following procedures in Engine Mechanical:
    • For incorrect, worn, or damaged basic engine parts, inspect the following:
       - The camshaft--Refer to Camshaft and Bearings Cleaning and Inspection .
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection .
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection .
    • Refer to Symptoms - Engine Mechanical for diagnosis procedures.
    • Inspect for excessive end play that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection . This could result in any of the following conditions.
       - A no start
       - A start and stall
       - Erratic performance

Additional Inspections
    • Inspect the exhaust system for possible restrictions. Inspect for the following:
       - Inspect the exhaust system for damaged or collapsed pipes.
       - Inspect the mufflers for heat distress or possible internal failure.
       - Inspect for possible plugged catalytic converters. Refer to Restricted Exhaust .
    • Electromagnetic interference (EMI) can cause an engine misfire condition. A sudden increase in indicated RPM parameter with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a condition exists.
    • Inspect the intake manifold and the exhaust manifold passages for casting flash.