GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2004 🢒 XLR 🢒 Engine 🢒 Engine Controls - 4.6L (LH2) 🢒 Hard Start

Inspection/Test

Action

DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies.

Preliminary
    • Refer to Symptoms - Engine Controls .
    • Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
    • Search for bulletins.
    • Verify that the driver is using the correct starting procedure as described in the owners manual.

Sensor/System
    • Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature Versus Resistance for resistance specifications.
    • Verify proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions .

Fuel System
    • Verify there is adequate fuel.
    • A faulty in-tank sender check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Solenoid Coil Test .
    • Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
    • Inspect for proper ignition voltage output with the J 26792 Spark Tester. 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 .
    • Determine the cause of the conditions before replacing the spark plugs.
    • Inspect for loose ignition coil grounds.
    • Inspect the ignition coils for cracks or carbon tracking.
    • Soak the secondary ignition with water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty.

Engine Mechanical

Inspect for the following conditions:

    • Excessive oil in combustion chamber or leaking valve seals--Refer Oil Consumption Diagnosis in Engine Mechanical.
    • Cylinder compression--Refer to Engine Compression Test in Engine Mechanical.
    • Improper valve timing
    • Worn rocker arms
    • Broken or worn valve springs
    • Combustion chambers for excessive carbon buildup--Clean the chambers using top engine cleaner. Follow the instructions on the can.
    • Incorrect or damaged 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

Additional
    • Inspect for a restricted exhaust. Refer to Restricted Exhaust in Engine Exhaust.
    • Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking, especially between the mass air flow (MAF) sensor and the throttle body.