Inspections
| Actions
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DEFINITION: Fuel ignites in the intake manifold or in the exhaust system, making
a loud popping noise.
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Preliminary Inspections
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• | Search for bulletins. |
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Fuel System
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• | Verify that each injector harness is connected to the correct injector
or cylinder. Relocate injector harnesses as necessary. |
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Sensor/System
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• | Inspect the air intake system and crankcase for air leaks. |
• | Use a scan tool in order to monitor the knock sensor (KS) system for excessive
spark retard activity. Refer to
Scan Tool Data List
. |
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Ignition System
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• | In order to properly inspect the spark plugs or to correct a condition,
refer to the following procedures: |
• | Remove spark plugs and inspect for the following conditions: |
- | Verify that the spark plugs are of the correct type. |
• | Inspect for proper ignition voltage output with the J 26792
HEI Spark Tester. |
• | An improper spark plug gap will cause a driveability condition. Gap the
spark plugs using a wire gauge gap tool. |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | Inspect for damaged or misaligned spark plug boots. |
• | Inspect the electronic ignition (EI ) module for proper ground connection. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the symptom occurred. If a misfiring cylinder can be located, use
the DTC P0300 table for diagnosis. Refer to
DTC P0300
. |
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Engine Cooling System
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• | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
• | Inspect the engine thermostat for proper operation and for the correct
heat range. Refer to
Thermostat Diagnosis
in Engine Cooling. |
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Engine Mechanical
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• | Inspect engine mechanical for the following conditions: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber or leaking valve seals |
- | For more information, refer to one or more of the following procedures
in Engine Mechanical: |
• | For incorrect basic engine parts. Inspect the following components: |
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Additional Inspections
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• | Visually and physically inspect the vacuum hoses for splits, kinks, and
proper connections and routing as shown on the Vehicle Emission Control Information
label. |
• | Inspect the intake manifold and the exhaust manifold passages for casting
flash. |
• | Inspect the exhaust system for the following possible restrictions: |
- | The exhaust system for damaged or collapsed pipes |
- | The mufflers for heat distress or possible internal failure |
- | The catalytic converter for being plugged--Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic interference (EMI) on the reference circuit can cause
an engine miss condition. A scan tool can usually detect EMI by monitoring the engine
RPM. A sudden increase in RPM with little change in actual engine RPM change may
indicate that EMI is present. If a problem exists, inspect for high voltage components
near the ignition control circuits. |
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