GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Riviera 🢒 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 .
    • Refer to Visual/Physical Checks in Symptoms .
    • Search for bulletins.

Fuel System
    • Check system fuel pressure. Refer to Fuel System Pressure Test (VIN 1) .
    • Check the fuel injectors.
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • 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 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 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
    • Check for conditions which cause an incorrect idle speed.
       - Throttle body tampering, excessive desposits, or damage.
       - Restricted air intake duct or dirty air cleaner element. Refer to Air Cleaner Element Replacement .
       - 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:
       - The EGR pipes and adapter for vacuum leaks.
       - Remove the EGR valve and check for a sticking pintle. Refer to Exhaust Gas Recirculation Valve Replacement .
    • Check the PCV valve for proper installation. Refer to Crankcase Ventilation System Inspection .
    • Check the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive. Refer to Transaxle Range Switch Valid Combinations table in DTC P0705 Trans Range Switch Circuit .
    • Check for the following conditions:
       - 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 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 J 26792 spark tester; a spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the coil(s), check for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and it's mate.

       - Coil(s) - Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

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

       - Spark Plug wires - Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, incorrect routing, or a resistance value greater than the specified value.

Spark Plug Wires Resistance
1000 to 1500 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 malfunctioning.

       - Malfunctioning ignition control module.
       - Ignition System Wiring - Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove spark plugs and check for the following conditions:
       - Fouled plugs
       - Cracks

   Important: If carbon tracking is detected on a component, replace that component and it's mate.

       - Check the spark plugs for carbon tracking on the porcelain and pitting on the plug wire contact.
       - Incorrect gap
       - Burned or damaged electrodes
       - Incorrect heat range
       -  Refer to Maintenance Items .
    • 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 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 signal

Engine Mechanical
    • Check engine mechanical for the following:
       - Check compression.
       - Sticking or leaking valves.
       - Worn camshaft lobe(s).
       - 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:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Engine Overhaul .

Additional Checks
    • Check the exhaust system for a possible restriction.
       - 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 and/or Exhaust System .
    •  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. Check routing of secondary ignition wires. Also, check ignition coils for cracks, carbon tracking, or signs of arcing.
    • Check for intake and exhaust manifold passages for casting flash. Refer to Intake Manifold Replacement and Exhaust Manifold Replacement .
    • Check for loose, worn, or broken motor mounts. Refer to Engine Mount Inspection .