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Inspections

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DEFINITION: A steady pulsation or jerking that follows engine speed, which is usually more pronounced as the 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 at low speed.

Preliminary
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the engine control system grounds for being clean, tight, and in the correct locations. Refer to Engine Controls Schematics . Ensure the resistance between the engine control module (ECM) housing and the battery negative cable is less than 0.5 ohms.
    • Verify that the ECM and ECM bracket fasteners are at the correct torque.
    • Remove the air filter element and inspect for restrictions. Refer to Air Cleaner Element Replacement .
    • Inspect the intake air duct and air cleaner outlet resonator for the following conditions:
       - Restrictions
       - Improperly installed hoses
       - Leaking
       - Collapsed hoses

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect the fuel system. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Test the items that cause an engine to run rich. For a rich condition, refer to DTC P2178 or P2180 and DTC P2188 or P2190 .
    • Test the items that can cause an engine to run lean. For a lean condition, refer to DTC P2177 or P2179 and DTC P2187 or P2189 .

Sensor/System

Monitor the knock sensor (KS) system for excessive spark retard activity with a scan tool. Refer to Knock Sensor (KS) System Description , DTC P0327 or P0332 , and DTC P0328 or P0333 .

Ignition System
    • Inspect for the correct installation of the ignition coil seals. Incorrect installation may allow water to enter the spark plug area. Inspect for moisture and corrosion.
    • Test for proper ignition voltage output with a J 26792 Spark Tester. If you suspect an ignition system condition, refer to Electronic Ignition (EI) System Diagnosis .
    • Remove the spark plugs and inspect for the following conditions:
       - Incorrect heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Refer to the following procedures:
    • If the spark plugs are gas, coolant, or oil fouled, determine the cause before replacing the spark plugs. Refer to the following procedures:
       - Test the items that cause an engine to run rich. For a rich condition, refer to DTC P2178 or P2180 and DTC P2188 or P2190 .
       - For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant .
       - For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis .
    • Inspect the spark plug boots and terminals for burning or micro-arcing, corrosion, and damage to the insulation.
    • Inspect the crankshaft position (CKP) sensor for the correct resistance. The sensor resistance may be out of range after a hot soak. Measure that the resistance remains within 700-1,200 ohms at all temperatures.

Engine Mechanical
    • Inspect for a condition with the camshaft actuator system. A camshaft actuator that is stuck in the full advance or retard position may cause this symptom. Refer to DTC P0011, P0014, P0021, or P0024 .
    • Inspect for the following engine mechanical conditions:
       - Excessive oil in combustion chamber or leaking valve seals
       - Incorrect cylinder compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Camshaft timing
       - Broken valve springs
       - Excessive carbon buildup in the combustion chambers--Clean the chambers with top engine cleaner. Follow the instructions on the can.
       - For more information, refer to the following procedures:
    • Inspect the following components for incorrect basic engine parts:
       - Camshafts
       - Cylinder heads
       - Pistons, connecting rods, or bearings.
       - Refer to the following procedures :

Additional
    • Inspect the following exhaust system components:
       - The exhaust system for damage
       - The mufflers for heat distress or possible internal failure
       - The three-way catalytic converters for restrictions
       - For more information, refer to Symptoms - Engine Exhaust .
    • Electromagnetic interference (EMI) on the CKP sensor signal circuits can cause an engine misfire condition. You can usually detect EMI with a scan tool by monitoring the engine speed parameter. A sudden increase in the engine speed parameter, with little change in actual engine speed indicates that EMI is present. Inspect for high voltage components near the ignition control circuits if a condition exists. Also, inspect the engine ground shield of the CKP sensor circuits.