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.
|
Preliminary
|
• | Inspect the powertrain control module (PCM) grounds for being
clean, tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
|
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 P0132 or P0152
. |
• | Inspect items that can cause an engine to run lean (long term
fuel trim near 24 percent. For a lean condition, refer to
DTC P0131 or P0151
. |
|
Sensor/System
| Use a scan
tool in order to monitor the knock sensor (KS) system for excessive spark
retard activity.
|
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. |
• | Test for proper ignition voltage output with J 26792
Spark Tester . |
• | Remove the spark plugs and check for the following: |
Refer to
Spark Plug Inspection
.
• | Determine the cause of the fouling before replacing the spark
plugs if the spark plugs are gas, coolant, or oil fouled. Refer to
DTC P0172 or P0175
for diagnosis of the rich
condition. Refer to
Spark Plug Inspection
for
diagnosis of coolant or oil fouled spark plugs. |
• | 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 |
• | 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. |
|
Engine Mechanical
|
• | Inspect engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber--Leaking valve seals.
Refer to
Oil Consumption Diagnosis
in Engine Mechanical 4.8L, 5.3L, 6.0L. |
• | For incorrect basic engine parts inspect the following: |
Refer to Engine/Engine Mechanical for diagnosis procedures.
|
Additional
Checks
|
• | Inspect the exhaust system for possible restrictions. Inspect
for the following: |
- | Inspect the exhaust system for damaged or collapsed pipes. |
- | Inspect the exhaust manifold for a collapsed inner wall. |
- | Inspect the mufflers for heat distress or possible internal failure. |
- | Inspect for possible plugged three-way catalytic converters by
comparing the exhaust system back pressure on each side of engine. Check
back pressure by removing secondary air injection
(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 condition exists. |
• | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
|