Checks
| Actions
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DEFINITION:
Fuel ignites in the intake manifold or in the exhaust system, making a loud
popping noise.
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Preliminary Checks
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• | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
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Fuel System
|
• | Inspect that each injector harness is connected to the correct
injector/cylinder according to the firing order (firing order: 1-8-7-2-6-5-4-3).
Relocate injector harnesses as necessary. |
|
Sensor/System
|
• | Test the secondary air injection (AIR) system. |
• | Inspect the air intake system and the crankcase for air leaks. |
• | Test the crankcase ventilation valve for proper operation. Place
a finger over inlet hole in valve end several times. The valve should snap
back. If not, replace the valve. |
• | Inspect for proper calibration of the speedometer. Connect Signal
Generator J 33431-B
to the
VSS electrical connector. Turn ON the ignition, the tester, and monitor
the speedometer. The speedometer should indicate 86 km/h
(54 mph). If not, refer to
Gauge System Check
in Instrument Panel, Gauges, and Console. |
|
Ignition System
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• | Test for proper ignition voltage output with spark tester J 26792
. |
• | Inspect for an intermittent ignition system malfunction in the
following circuits: |
- | Ignition control circuit |
- | Use the Snapshot feature on the scan tool in order to help locate
an intermittent ignition failure. |
• | Remove the spark plugs and inspect for the following conditions: |
• | To properly inspect the spark plugs or to correct a problem, refer
to the following procedure in Engine Electrical: |
• | An improper spark plug gap causes a driveability concern. Gap
the spark plugs using a wire gauge gap tool. Refer to
Spark Plug Replacement
. |
• | Visually/physically inspect secondary ignition for the following: |
- | Ignition wires arcing to ground |
- | Ignition wires for proper routing |
- | Ignition coils for cracks or carbon tracking |
• | Wet down the secondary ignition system with water from a spray
bottle. Wetting down the secondary ignition system may help locate damaged
or deteriorated components. Look/listen for arcing or misfiring
as you apply the water. |
|
Engine
Cooling System
|
• | Inspect the engine thermostat for proper operation and correct
heat range. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber-Leaking valve seals |
• | For more information, refer to one or more of the following procedures
in Engine Mechanical-5.7L: |
• | For incorrect basic engine parts, inspect the following components: |
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Additional Checks
|
• | Visually/physically inspect the vacuum hoses for splits, kinks,
and proper connections and routing as shown on Vehicle Emission Control Information
label. Refer to
Emission Hose Routing Diagram
. |
• | Test the transmission torque converter clutch (TCC) for proper
operation. The scan tool should indicate an RPM drop when the TCC is commanded
ON. Refer to
Torque Converter Diagnosis
in Automatic Transmission-4L60E. |
• | Inspect the following exhaust system components for possible restrictions: |
- | The exhaust system for physical damage |
- | The exhaust manifold for a collapsed inner wall |
- | The mufflers for heat distress or possible internal failure |
- | The Three-Way catalytic converters for possible plugged pipes
by comparing the exhaust system back pressure on each side of engine |
• | For more information, refer to the following procedures in Engine
Exhaust: |
• | Electromagnetic interference (EMI) on the reference circuit can
cause an engine miss condition. A scan tool can usually detect EMI by monitoring
the engine RPM. A sudden increase in RPM with little change in
actual engine RPM change, may indicate that EMI is present. If
a problem exists, inspect for high voltage components near ignition
control circuits. |
• | Inspect for faulty engine mounts. Refer to
Engine Mount Replacement
in Engine Mechanical-5.7L for inspection
of the mounts. |
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