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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 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 Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Verify that the engine control module (ECM) 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. Refer to Air Cleaner Element Replacement . Replace as necessary.

Fuel System
    • Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Solenoid Coil Test .
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for proper operation of the evaporative emission (EVAP) control system . Refer to Evaporative Emission Control System Description .
    • 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:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Water intrusion in the heated oxygen sensor (HO2S) connector
       - Engine oil contaminated by fuel
       - An EVAP canister purge condition
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Leaking fuel injectors--Refer to Fuel System Diagnosis .
       - Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions .
       - Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions .
       - Blockage on the inlet screen of the MAF sensor.
       - 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--Refer to Air Cleaner Element Replacement .
    • Inspect for the following conditions that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

       - Water intrusion in the HO2S connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
       - Vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .
       - Inspect for proper operation of the MAP sensor. Refer to Scan Tool Data Definitions .
       - Inspect for proper operation of the MAF sensor. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
       - Vacuum hoses that are split, kinked, or improperly connected

Sensor/System
    • Monitor the knock sensor (KS) system for excessive spark retard activity, with a scan tool.
    • Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed , or leaking especially between the MAF sensor and the throttle body.
    • Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature Versus Resistance .
    • Inspect for a vacuum leak.
    • Inspect the crankcase ventilation operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.

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.
    • Performing a Cylinder Balance Test with a scan tool may also help isolate which cylinder may be misfiring.
    • Test for proper ignition voltage output. Refer to Electronic Ignition (EI) System Diagnosis .
    • 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 Ignition System Specifications .
    • Determine the cause of the fouling before replacing the spark plugs.
    •  Visually and physically inspect for the following conditions:
       - The spark plug boots for signs of arcing, cracks, carbon tracking, or damage
       - The spark plug boots 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
       - Worn rocker arms--Refer to Valve Rocker Arms 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:
       -  Engine Compression Test
       -  Symptoms - Engine Mechanical
       -  Oil Consumption Diagnosis
    •  For incorrect basic engine parts inspect the following components:
       - The camshaft--Refer to Camshaft 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

Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnostic procedures.

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. Refer to Intake Manifold Cleaning and Inspection or Exhaust Manifold Cleaning and Inspection - Left Side and Exhaust Manifold Cleaning and Inspection - Right Side in Engine Mechanical