Inspections
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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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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. |
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Ignition System
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• | Inspect the coils for cracks, carbon tracking/arcing. |
• | Inspect spark plug boots for signs of arcing , cracks, carbon tracking,
or damage. |
• | Remove spark plugs and inspect for the following conditions: |
• | Determine the cause of the fouling before replacing the spark plugs. |
• | 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 the water. |
• | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the misfire occurred. |
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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 |
• | 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 transmission torque converter clutch (TCC) operation. The
scan tool should indicate an RPM drop when the TCC is commanded ON. |
• | Inspect the exhaust system for possible restrictions. Inspect 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 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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