GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 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 in Symptoms before starting.
    • Refer to Visual/Physical Checks in Symptoms .
    • Search for bulletins.

Fuel System
    • Check system fuel pressure. Refer to Fuel System Pressure Test (VIN K) .
    • Check the fuel injectors using the following procedures:
       -  Fuel Injector Balance Test
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check 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 Fuel Trim System Rich .
    • Check 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 Fuel Trim System Lean .
    • Check for fuel in the Fuel Pressure Regulator vacuum hose.

Sensor/System
    • Check for conditions which cause an incorrect idle speed.
       - Throttle body tampering, excessive deposits, or damage. Refer to Fuel Metering System Component Description .
       - Restricted air intake system. Refer to Air Intake System Description .
       - Large vacuum leak.
    • Check the TP sensor and related circuit wiring. Refer to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage .
    • Check the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    • Check the PCV Valve for proper operation. Refer to Crankcase Ventilation System Description .
    • Check the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive. Refer to Range Reference in Automatic Transaxle - 4T65-E.
    • Check 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 theJ 26792 spark tester to engine ground.
       - Connect one end of a spark plug wire to the spark tester, leave the other end of the spark plug wire to the coil being tested.
       - Connect one end of another spark plug wire to the other coil tower, connect the other end of the spark plug wire to ground.
       - Crank the engine while observing the spark tester, a spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the plug, check for the following conditions:
       - Coils - Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

Coil Resistance
5000-8000 ohms (5K-8K 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
600 ohms per/ft.

   Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. 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 check for the following components:
       - Fouled plugs
       - Cracks

   Important:: If carbon tracking is detected on any component replace that component and it's mate. Carbon tracking on the porcelain and pitting on the plug wire contact.

       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach. Refer to Spark Plug Usage in Engine Electrical.
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Check 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
    • Check engine mechanical for the following:
       - Check compression
       - 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
       - Low cylinder compression
    • For incorrect basic engine parts inspect the following components:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to Engine Compression Test and Cylinder Leakage Test in Engine Mechanical.

Additional Checks
    • Check exhaust system for possible restrictions:
       - Inspect exhaust system for damaged or collapsed pipes.
       - Inspect mufflers for heat distress or possible internal failure.
       - For possible plugged three-way catalytic converter. Refer to Restricted Exhaust System Check .
    •  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 problem exists, check routing of secondary ignition wires, high voltage components near ignition control circuits.
    • Check for intake and exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection and Exhaust Manifold Cleaning and Inspection .
    • Check for faulty motor mounts. Refer to Engine Mount Inspection in Engine Mechanical.