Inspection/Test
| Actions
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DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust system, making loud
popping noise.
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Preliminary
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Sensor/System
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| • | Inspect for the following intermittent ignition system conditions: |
| - | Monitor the 24 X crankshaft position (CKP) and camshaft
position (CMP) sensors on scan tool. If both are not responding, test the
sensor feed circuit. Both sensors use a separate feed circuit but are internally
connected to power. Test all 24 X and CMP sensor circuits for intermittents.
Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| - | Monitor the 3 X parameter on the scan tool. If the 3 X
is not responding, inspect the 7 X CKP sensor and circuits for intermittents.
Inspect the ignition control (IC) circuit, bypass circuit, 3 X reference
high circuit, and the 3 X reference low circuit for intermittents.
If these circuits become open or shorted, the conditions may not set a DTC
immediately, but are capable of causing driveability complaints. Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Inspect the mass air flow (MAF) sensor conditions. Ensure that
the MAF sensor honeycomb is not damaged. |
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Fuel System
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| • | Ensure each injector harness is connected to the correct injector/cylinder. |
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Ignition System
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| • | Inspect for proper ignition voltage output using the following
steps: |
| 1. | Attach the J 26792
Spark Tester to engine ground. |
| 2. | Connect the spark plug end of the spark plug wire to the J 26792
. Connect the other end
of the spark plug wire to the coil being tested. |
| 3. | Connect the spark plug end of the companion spark plug wire to
ground. |
The companion spark plug wire is the wire attached to the corresponding
coil tower.
| 4. | Crank the engine while observing the J 26792
. A spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If spark is not present at the coils, inspect for the following
conditions: |
| - | Coils--Cracks, carbon tracking/arcing, or a resistance value
outside the specified range. |
Coil Resistance
5000-8000 ohms (5K-8K ohms) | - | Spark Plug wires--Signs of arcing, cross firing, cracks,
carbon tracking, plug boot damage, pinched, improper routing, or a resistance
value outside the specified range. |
Spark Plug Wire Resistance
1 968 ohms per meter (600 ohms per foot).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent condition. Ignition voltage will arc to ground
when a secondary component is faulty.
|
| - | Defective ignition module. |
| - | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and inspect for the following conditions: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If the spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. Refer to
Spark Plug Inspection
. |
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Engine Mechanical
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| • | Inspect the engine for the following conditions: |
| - | Sticking or leaking valves |
| - | Excess oil in the combustion chamber--Inspect for leaking
valve seals. |
| - | Low cylinder compression |
| • | Inspect for incorrect engine parts, such as the following basic
components: |
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Additional
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| • | Inspect intake and exhaust manifolds for casting flash. |
| • | Inspect the exhaust system for possible restriction: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
| - | For possible plugged catalytic converter. |
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