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 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. |
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Fuel System
|
| • | Ensure that each injector harness is connected to the correct
injector/cylinder. |
|
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
5,000-8,000 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
3,000 ohms per foot (9,868 ohms per meter).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition voltage arcs 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 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--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 the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Test for possible catalytic converter restrictions by testing
the exhaust system back pressure. |
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