Checks
| Actions
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DEFINITION: Fuel ignites in the intake manifold or in
the exhaust system, making a loud popping noise.
|
Preliminary Checks
|
• | Inspect the powertrain control module (PCM) grounds for being
clean, tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
|
Fuel System
|
• | Verify that each injector harness is connected to the correct
injector or cylinder according to the firing order: 1-8-7-2-6-5-4-3.
Relocate injector harnesses as necessary. |
|
Sensor/System
|
• | Inspect the air intake system and crankcase for air leaks. |
• | Inspect the crankcase ventilation valve for proper operation.
Place a finger over the inlet hole in the valve end several times. The valve
should snap back. If not, replace the valve. |
• | Inspect for proper calibration of the speedometer. Connect J 33431-B
Signal Generator to
the vehicle speed sensor (VSS) electrical connector. Ignition ON, tester
ON and monitor the speedometer. The speedometer should
indicate 86 km/h (54 mph). |
|
Ignition System
|
• | Inspect for proper ignition voltage output with J 26792
Spark Tester . |
• | Inspect for an intermittent ignition system malfunction in the
following circuits: |
- | Intermittent ignition control circuit |
- | Use the scan tool's Snapshot feature in order to help locate an
intermittent ignition failure. |
• | An improper spark plug gap will cause a driveability problem.
Gap the spark plugs using a wire gage gap tool. Refer
to
Spark Plug Replacement
. |
• | Determine the cause of the fouling before replacing the spark
plugs if the spark plugs are gas, coolant, or oil fouled. Refer to
Spark Plug Inspection
for diagnosis of fouled
spark plugs. |
• | Inspect the secondary ignition for the following conditions: |
- | Ignition wires arcing to ground |
- | Ignition wires for proper routing |
• | Wetting down the secondary ignition system with water from a spray
bottle may help locate damaged or deteriorated components. Look and listen
for arcing or misfiring as you apply water. |
|
Engine Cooling System
|
• | Inspect the engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
• | Inspect the engine thermostat for proper operation and for the
correct heat range. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
• | Check engine mechanical for the following conditions: |
- | Sticking or leaking valves |
• | Inspect the following components for incorrect basic engine parts: |
• | Refer to the appropriate procedures in Engine Mechanical 8.1L
for diagnosis procedures. |
|
Additional Checks
|
• | Inspect the vacuum hoses for splits, kinks, and proper connections
and routing as shown on the Vehicle Emission Control Information
label. |
• | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
• | Inspect the following components of the exhaust system for possible
restrictions: |
- | The exhaust system for damaged or collapsed pipes |
- | 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 conditions--Compare
the exhaust system back pressure on each side of engine. Refer to
Restricted Exhaust
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 the ignition control circuits. |
• | Inspect the park/neutral position (PNP) switch operation. |
• | Inspect the intake manifold and the exhaust manifold passages
for casting flash |
|