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 crankshaft position (CKP) sensor and the camshaft
position (CMP) sensors on a scan tool. If neither sensor is responding, test
the sensor feed circuit. Both sensors use a separate feed circuit but are
internally connected to power. Test the 24X sensor circuits and the 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 7X CKP sensor and the circuits for intermittents. Inspect the
ignition control (IC) circuit, the bypass circuit, the 3X reference high
circuit, and the 3X reference low circuit for intermittents. If these circuits
become open or shorted a DTC may not set immediately, but the sensors 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. 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
and cylinder. |
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Ignition System
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| • | Inspect for the 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
spark tester. 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
spark tester. 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: |
| - | Check the coils for cracks, carbon tracking or arcing, or a resistance
value outside the specified range. |
Coil Resistance
5,000-8,000 ohms | - | Check the spark plug wires for signs of arcing, cross-firing,
cracks, carbon tracking, plug boot damage, pinching, 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 problem. The ignition voltage will arc to ground
when a secondary component is faulty.
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| - | Test for a faulty ignition module. |
| - | Inspect the ignition system wiring for a loose ignition module
feed or ground connection, or damaged system wiring. |
| • | Remove the 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 Visual Diagnosis
in Engine Electrical. |
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Engine Mechanical
| Inspect or test for the following engine mechanical conditions:
| • | An incorrect compression |
| • | Any sticking or leaking valves |
| • | Any worn camshaft lobes |
| • | An improper valve timing |
| • | Any broken valve springs |
| • | Any excessive oil in the combustion chambers or leaking valve
seals |
| • | Inspect the following components for incorrect basic engine
parts: |
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Additional
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| • | Inspect the intake manifold and the exhaust manifold for casting
flash. |
| • | Inspect the exhaust system for restrictions: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or internal failure. |
| - | Inspect for a plugged catalytic converter. |
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