GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Impala 🢒 Engine 🢒 Engine Electrical 🢒 Cuts Out, Misses

Checks

Action

DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases.

Preliminary
    • Refer to Important Preliminary Checks Before Starting.
    • Refer to Visual/Physical Checks.
    • Search for bulletins.

Fuel System
    • Test system fuel pressure. Refer to Fuel System Diagnosis .
    • Test the fuel injectors using the following tests:
       - Refer to Fuel Injector Solenoid Coil Test .
       - Refer to Fuel Injector Balance Test with Tech 2 .
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect items which can cause an engine to run rich, long term fuel trim significantly in the negative range. Refer to Diagnostic Aids for DTC P0172 .
    • Inspect items that can cause an engine to run lean, long term fuel trim significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 .
    • Inspect for fuel in the fuel pressure regulator vacuum hose.

Sensor/System
    • Inspect for conditions which cause an incorrect idle speed.
       - Throttle body tampering, excessive deposits, or damage
       - Restricted air intake system--Refer to Air Intake System Description .
       - Large vacuum leak
    • Test the TP sensor and related circuit wiring. Refer to DTC P0123 .
    • Test the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    • Test the PCV valve for proper operation.
    • Test the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive.
    • Inspect the following for damage:
       - Bent harmonic balancer interrupter rings
       - Damaged crankshaft position sensor

Ignition System
    • Check for proper ignition voltage output using the following steps:
       - Clip the J 26792 Spark Tester to engine ground.
       - Connect one end of a spark plug wire to the J 26792 . Connect the other end of the spark plug wire to the coil being tested.
       - Connect another spark plug wire between the remaining tower of the coil being tested and ground.
       - Crank the engine while observing the J 26792 . A spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the coils, inspect for the following conditions:
       - Coils--Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range

Coil Resistance
5,000-8,000 ohms

       - Spark plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range.

Spark Plug Wire Resistance
9,840 ohms (3,000 ohms per ft)

   Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent condition. Ignition components will arc to ground when a secondary component is faulty.

       - Defective module
       - Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring
    • Remove spark plugs and inspect for the following:
       - Fouled plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Test for the following intermittent ignition system conditions:
       - Intermittent CKP 18X signal
       - Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor
       - Intermittent 3X reference signal
       - Intermittent camshaft position signal

Engine Mechanical
    • Test and inspect engine mechanical for the following:
       - Test compression
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Bent push rods
       - Worn rocker arms
       - Broken valve springs
       - Excess oil in combustion chamber--Inspect for leaking valve seals.
       - Low cylinder compression
    • Inspect for incorrect engine parts, such as the following basic components:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to Symptoms - Engine Mechanical in Engine Mechanical.

Additional Checks
    • Test exhaust system for possible restrictions. Inspect for the following:
       - The exhaust system for damaged or collapsed pipes.
       - The mufflers for heat distress or possible internal failure.
       - For possible plugged three-way catalytic converter--Refer to Restricted Exhaust in Engine Exhaust.
    •  An engine miss condition can be caused by electromagnetic interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a condition exists, inspect routing of secondary ignition wires, high voltage components near ignition control circuits.
    • Inspect for intake and exhaust manifold passages for casting flash.
    • Inspect for faulty motor mounts.