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) and camshaft position
(CMP) sensors 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 24X 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 7X CKP sensor and circuits for intermittents. Inspect the ignition
control (IC) circuit, bypass circuit, 3X reference high circuit, and the
3X reference low circuit for intermittents. If these circuits become open,
or shorted 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. |
|
Fuel
System
|
| • | Ensure each injector harness is connected to the correct injector
and/or cylinder. |
|
Ignition
System
|
| • | 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. |
| | 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.
|
| • | If spark is not present at the coils, inspect the following components
for the specified conditions: |
| - | Coils--Cracks, carbon tracking and/or arcing, or a resistance
value outside the specified range |
Coil Resistance
5000-8000 ohms (5K-8K ohms)
Spark Plug Wire Resistance
9868 ohms per meter (3000 ohms per foot)
| • | A resistance value outside the specified range |
| - | Defective ignition module |
| - | Ignition system wiring--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 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
. |
|
Engine
Mechanical
| Inspect engine mechanical for the following conditions:
| • | Sticking or leaking valves |
| • | Excessive oil in combustion chamber due to leaking valve seals |
| • | Low cylinder compression |
| • | Inspect the following components for incorrect basic engine parts: |
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Additional
|
| • | Inspect the intake and exhaust manifolds for casting flash. |
| • | Inspect the following components of the exhaust system for possible
restrictions: |
| - | Inspect for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Test for possible plugged catalytic converter by testing the
exhaust system back pressure. |
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