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 24X crank sensor and the CMP sensor signal present parameters
on the 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 CKP sensor A and CMP sensor circuits for intermittents. Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring
Systems. |
| - | Monitor the 3X parameter on the scan tool. If the 3X is not responding,
inspect the CKP sensor B and circuits for intermittents. Inspect the ignition
control (IC) circuit, IC timing control circuit, low resolution engine speed signal
circuit and the low reference circuit for intermittents. If these circuits become
open, or shorted, they may not set a diagnostic trouble code (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
. Leave the other end of the spark plug wire
connected 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
9 686 ohms per meter (3,000 ohms per foot)
| | Important: : Spraying the secondary ignition wires with a light mist of water may help locate
an intermittent problem. Ignition voltage will arc to ground when a secondary component
is faulty.
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| - | 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 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
| Inspect engine mechanical for the following conditions:
| • | Sticking or leaking valves |
| • | Excessive oil in combustion chamber--Leaking valve seals |
| • | Low cylinder compression |
| • | For incorrect basic engine parts--Inspect the following 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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