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. |
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Ignition System
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• | Inspect for proper ignition voltage output with the
J 26792
Spark Tester . |
• | Remove spark plugs and inspect for the following: |
Refer to
Spark Plug Inspection
.
• | Determine the cause of the fouling before replacing the spark plugs. Refer to
Spark Plug Inspection
for diagnosis. |
• | Visually and physically inspect secondary ignition for the following: |
- | Ignition wires arcing to ground |
- | Ignition coils arcing to ground |
• | 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. 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
. |
• | Inspect the engine thermostat for proper operation and for the correct heat range. Refer to
Thermostat Diagnosis
. |
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Engine Mechanical
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• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
• | For incorrect basic engine parts--Inspect the following: |
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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 transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Refer to
Diagnostic System Check - Vehicle
. |
• | Inspect the exhaust system for possible restrictions. Inspect the following: |
- | Inspect the exhaust system for damaged or collapsed pipes. |
- | Inspect the mufflers for heat distress or possible internal failure. |
• | 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. |
• | Inspect the intake manifold and the exhaust manifold passages for casting flash |
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