GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Uplander Ext. 🢒 Engine 🢒 Engine Controls - 3.5L (LX9) 🢒 Cuts Out, Misses

Inspections

Action

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 Inspections Before Beginning in Symptoms - Engine Controls .
    • Search for bulletins.
    • Verify that the powertrain control module (PCM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
    • Remove the air filter element and inspect for dirt and for restrictions.

Fuel System
    • Test for restricted fuel or incorrect fuel pressure. Refer to Fuel Pump Electrical Circuit Diagnosis .
    • Inspect for proper operation of the evaporative emission (EVAP) control system.
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect for the following conditions that may cause the engine to run rich:
       - Water intrusion in the heated oxygen sensor (HO2S) connector
       - Engine oil contaminated by fuel
       - An EVAP canister purge condition
       - Leaking fuel injectors--Refer to Fuel System Diagnosis .
       - For proper operation of the manifold absolute pressure (MAP) sensor--Refer to Manifold Absolute Pressure Sensor Diagnosis .
       - For proper operation of the mass air flow (MAF) sensor--Refer to Scan Tool Data List and Scan Tool Data Definitions .
       - Vacuum hoses that are split, kinked, or improperly connected
       - An air intake duct that is collapsed or restricted
       - An air filter that is dirty or restricted.
    • Inspect for the following conditions that may cause the engine to run lean:
       - Water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
       - Vacuum leaks
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Sensor/System
    • Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity.
    • Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAP sensor and the throttle body.
    • Inspect for a vacuum leak.
    • Inspect the exhaust gas recirculation (EGR) system for proper operation.

Ignition System
    • Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a misfiring cylinder can be located, use the DTC P0300 table for diagnosis. Refer to DTC P0300 .
    • Test for proper ignition voltage output with the J 26792 Spark Tester .
    • Remove the spark plugs and inspect for the following conditions:
       - 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 gage gap tool . Refer to Spark Plug Wire Replacement and Ignition System Specifications .
    • Determine the cause of the fouling before replacing the spark plugs.
    •  Visually and physically inspect the secondary ignition for the following conditions:
       - The spark plug wires for signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range--Refer to Ignition System Specifications .
       - The ignition wires for proper engagement to spark plug
       - The ignition coils for cracks or carbon tracking

Engine Mechanical
    • Inspect engine mechanical for the following conditions:
       - Test compression--Refer to Engine Compression Test in Engine Mechanical.
       - Sticking or leaking valves
       - Worn camshaft lobes
       - Valve timing
       - Bent push rods--Refer to Valve Rocker Arm and Push Rod Cleaning and Inspection in Engine Mechanical.
       - Worn rocker arms--Refer to Valve Rocker Arm and Push Rod Cleaning and Inspection in Engine Mechanical.
       - Broken valve springs--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
       - Excessive oil in combustion chamber, leaking valve seals
    • For more information refer to one of the following procedures in Engine Mechanical:
       -  Engine Compression Test
       -  Symptoms - Engine Mechanical
       -  Oil Consumption Diagnosis
    •  For incorrect basic engine parts inspect the following components:
       - The camshaft--Refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical.
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection in Engine Mechanical.
    • Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions:
       - A no start
       - A start and stall
       - Erratic performance

Additional Inspections
    • Inspect the exhaust system for possible restrictions. Inspect for the following conditions:
       - The exhaust system for damaged or collapsed pipes
       - The mufflers for heat distress or possible internal failure
       - For possible plugged catalytic converters--Refer to Restricted Exhaust in Engine Exhaust.
    • Electromagnetic interference (EMI) on the reference circuit can cause an engine misfire condition. A sudden increase in indicated RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a condition exists.
    • Inspect the intake manifold and the exhaust manifold passages for casting flash.