GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 Cuts Out, Misses

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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 Checks Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Check the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .
    • Remove the air filter element and check for dirt or for being restricted. Refer to Air Cleaner Element Replacement . Replace as necessary.

Fuel System
    • Check the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    •  Check for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    •  Check for a restricted fuel filter. Refer to Fuel System Diagnosis .
    •  Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check items that cause an engine to run rich long term fuel trim near -13 percent. For a rich condition, refer to DTC P0172 or P0175 .
    • Check items that can cause an engine to run lean (long term fuel trim near 24 percent. For a lean condition, refer to DTC P0171 or P0174 .

Sensor/System

Use a scan tool in order to monitor the knock sensor system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .

Ignition System
    • Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
    • Check for proper ignition voltage output with J 26792 Spark Tester .
    • Remove the spark plugs and check for the following:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • Refer to Spark Plug Inspection .
    • An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .
    • Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to one of the following procedures:
       - For diagnosis of the rich condition, refer to DTC P0172 or P0175 .
       - For diagnosis of coolant or oil fouled spark plugs, refer to Spark Plug Inspection .
    • Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a cylinder can be located with a misfire, refer to DTC P0300 for diagnosis.
    • Check for loose ignition coil grounds. Refer to Engine Controls Schematics .
    •  Visually and physically inspect the secondary ignition for the following:
       - Ignition wires arcing to ground
       - Ignition wires for proper engagement to spark plug
       - Ignition coils for cracks or carbon tracking

Engine Mechanical
    • Check engine mechanical for the following:
       - Check compression--Refer to Engine Compression Test in Engine Mechanical-8.1L.
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Bent push rods
       - Worn rocker arms
       - Broken valve springs
       - Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical-8.1L .
    • Inspect the following components for incorrect basic engine parts:
       -  The Camshaft
       -  The Cylinder heads
       -  The Pistons, etc.

Refer to the appropriate procedures in Engine Mechanical-8.1L for diagnosis procedures.

Additional Checks
    • Inspect the following components of the exhaust system for possible restrictions:
       - The exhaust system for damaged or collapsed pipes
       - The exhaust manifold for a collapsed inner wall
       - The mufflers for heat distress or possible internal failure
       - The three-way catalytic converters for possible plugged conditions--Compare the exhaust system back pressure on each side of engine. Check back pressure by removing AIR check valves near exhaust manifolds. Refer to Restricted Exhaust in Engine Exhaust.
    • Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition A sudden increase in indicated RPM with little change in actual engine RPM change indicates EMI is present. Check for high voltage components near ignition control circuits if a problem exists.
    • Check the intake manifold and the exhaust manifold passages for casting flash.