Checks
| Action
|
DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced
as engine load increases. This condition is not normally
felt above 1,500 RPM or 48 km/h (30 mph).
The exhaust has a steady spitting sound at idle or
low speed.
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Preliminary
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Fuel
System
|
• | Inspect items that cause an engine to run rich long term fuel
trim near -13 percent. For a rich condition, refer to
DTC P0172 or P0175
. |
• | Inspect items that can cause an engine to run lean, long term
fuel trim near 24 percent. For a lean condition, refer to
DTC P0171 or P0174
. |
|
Sensor/System
| Use a scan
tool in order to monitor the knock sensor (KS) system for excessive spark
retard activity. Refer to
Knock Sensor (KS) System Description
.
|
Ignition System
|
• | 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 and listen for arcing
or misfiring as you apply water. |
• | Inspect for proper ignition voltage output with J 26792
Spark Tester . |
• | Remove the spark plugs and inspect for the following: |
• | 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 one
of the following procedures: |
• | Monitor the Misfire Current Counters while driving the vehicle
in the conditions that the misfire occurred. If a cylinder can be located
with a misfire, use the DTC P0300 table for diagnosis. |
• | Visually and physically inspect the secondary ignition for the
following: |
- | Ignition wires arcing to ground |
- | Ignition wires for proper engagement to spark plug |
- | Ignition coils for cracks or carbon tracking |
|
Engine
Mechanical
|
• | Inspect the engine for the following mechanical 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.
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Additional Checks
|
• | 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 3-way catalytic converters (TWC) for possible plugged conditions--Compare
the exhaust system back pressure on each side of engine. Check back
pressure by removing AIR check valves near exhaust manifolds.
Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Electromagnetic interference (EMI) on the reference circuit can
cause an engine miss condition a sudden increase in indicated RPM with
little change in actual engine RPM change indicates
EMI is present. Check for high voltage components near ignition
control circuits if a problem exists. |
• | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
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