Checks
| Action
|
DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced as
engine load increases.
|
Preliminary
|
• | Refer to
Symptoms
, Important
Preliminary Checks Before Starting. |
• | Check the PCM grounds for being clean, tight and in their proper
locations. |
• | Remove and check the air filter element for dirt, or for being
restricted. Replace as necessary. |
|
Fuel System
|
• | Perform an injector balance test. |
• | Check for a restricted fuel filter. |
• | Check items which can cause an engine to run rich (long term fuel
trim near -99%). |
• | Check items that can cause an engine to run lean (long term fuel
trim near 100%). |
|
Sensor/System
|
• | Using a scan tool, monitor the KS system for excessive spark
retard activity. |
• | Check the EGR system for proper operation. |
|
Ignition System
|
• | Remove the spark plugs and check for the following: |
• | An improper spark plug gap will cause a driveability problem.
The spark plug gapping should be done using a wire gauge gap tool (J 41319).
If spark plugs are gas or oil fouled, the cause of the fouling must be
determined before replacing the spark plugs. |
• | Check the plugs/coils for signs of arcing, cracks or carbon tracking. |
• | Check for loose ignition control module grounds. |
• | Check the spark plugs for proper heat range. |
|
Engine Mechanical
| Check for the following conditions:
• | Sticking or leaking valves. |
• | Excessive oil in combustion chamber-Leaking valve seals |
• | Low cylinder compression. |
• | incorrect basic engine parts. Inspect the following: |
Refer to Base Engine Misfire Diagnosis
for diagnostic
procedures.
|
Additional Checks
|
• | Check for improper harness routing. An engine miss condition can
be caused by Electromagnetic Interference (EMI) on some engine controls circuits.
Use the scan tool to check for erratic sensor values or excessive changes
in indicated RPM with little change in actual engine RPM. This may indicate
EMI is present. If a problem exists, check for improper routing of the
harness near high voltage components (Ignition Components) or high current
components (alternator, motors, solenoids etc.). |
• | Check the charging system. a bad diode in the alternator can allow
AC noise to enter the electrical system. This may affect the engine controls
system operation. Refer to
Charging System Check
. |
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