GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Firebird 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Cuts Out, Misses

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

Preliminary
    • Refer to the Symptoms - Engine Controls .
    • Search for bulletins.

Fuel System
    • Test system fuel pressure. Refer to Fuel System Diagnosis , and to Fuel Pump Electrical Circuit Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test items which can cause an engine to run rich, with the long-term fuel trim (FT) significantly in the negative range. Refer to Diagnostic Aids for DTC P0172 or P0175 .
    • Test items that can cause an engine to run lean, with the long-term FT significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 or P0174 .
    • Inspect for fuel in the fuel pressure regulator vacuum hose. If fuel is present, replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .

Sensor/System
    • Inspect for conditions which cause an incorrect idle speed:
       - Throttle body tampering, excessive deposits, or damage
       - Restricted air intake duct or dirty air cleaner element--Refer to Air Cleaner Element Replacement .
       - Large vacuum leak
    • Test the electronic throttle control and inspect the related circuit wiring.
    • Test the exhaust gas recirculation (EGR) system:
       - The EGR pipes and adapter for vacuum leaks.
       - Remove the EGR valve and inspect for a sticking pintle. Refer to Exhaust Gas Recirculation Valve Replacement .
    • Inspect the positive crankcase ventilation (PCV) valve for proper installation:
        1. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.
        2. Test the transaxle range switch input with the vehicle in drive, and the gear selector in drive, or in overdrive.
        3. Inspect for the following conditions:
   • Bent harmonic balancer interrupter rings
   • Damaged crankshaft position (CKP) sensor

Ignition System
    • Test 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 spark tester. 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 spark tester, a spark should be observed.
       - Repeat the above steps for each coil.
    • If adequate spark is not present at the coils, test for the following conditions:
       - Coils--Evidence of carbon tracking or arcing, cracks in the coils, or a resistance value outside the specified range:

Coil Secondary Resistance
5000-8000 ohms (5K-8K ohms)

   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 malfunctioning.

       - Spark plug wires--Inspect for the following conditions:
   • Evidence of arcing
   • Evidence of cross firing
   • Cracks
   • Carbon tracking
   •  Plug boot damage
   • Pinched wires
   •  Incorrect routing
       - Spark plug wires--Inspect for a resistance value more than the specified value:

Spark Plug Wires Resistance
3280-4921 ohms/meter (1000-1500 ohms/ft)

       - Malfunctioning ignition control module
       - Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove spark plugs and test for the following conditions:
       - Fouled plugs
       - Cracks
       - Wear
       - Incorrect gap
       - Burned or damaged electrodes
       - Incorrect heat range
    • 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 crankshaft position (CKP) sync or 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 (CMP) signal

Engine Mechanical
    • Test the following:
       - Engine 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 Base Engine Misfire without Internal Engine Noises in Engine Mechanical.

Additional Tests
    • Test the exhaust system for a possible restriction.
       - Inspect exhaust system for damaged or collapsed pipes.
       - Inspect mufflers for heat distress or possible internal failure.
       - Plugged three-way catalytic converter--Test for possible plugged conditions. 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 or decrease in RPM with little change in actual engine RPM change indicates that EMI is present. Inspect the routing of secondary ignition wires. Also, inspect the ignition coils for cracks, carbon tracking, or signs of arcing.
    • Inspect for intake and exhaust manifold passages for casting flash.
    • Inspect for loose, worn, or broken motor mounts.