Checks
| Action
|
DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced as
engine load increases.
|
Preliminary
|
• | Verify that the powertrain control module (PCM) grounds are clean,
tight, and in the correct locations. |
• | Inspect the air filter element for dirt and restrictions. Replace
the element as necessary. |
|
Fuel
System
|
• | Perform the fuel injector balance test. |
• | Inspect for a restricted fuel filter. |
• | Inspect items that can cause an engine to run rich. |
• | Inspect items that can cause an engine to run lean. |
|
Sensor
and System
|
• | Using a scan tool, monitor the knock sensor (KS) system for any
excessive spark retard activity. |
• | Inspect the exhaust gas recirculation (EGR) system for the correct
operation. |
|
Ignition
System
|
• | Remove the spark plugs. Inspect for the following: |
• | An improper spark plug gap will cause a driveability problem.
The spark plug gapping should be done with a wire gage gap tool. If the
spark plugs are gas or oil fouled, the cause of the fouling must be
determined before replacing the spark plugs. |
• | Inspect the plugs and the coils for signs of arcing, cracks, or
carbon tracking. |
• | Inspect for any loose ignition control module grounds. |
• | Inspect the spark plugs for the correct heat range. |
|
Engine
Mechanical
| Inspect for the following conditions:
• | Any sticking or leaking valves |
• | Any worn camshaft lobes |
• | An incorrect valve timing |
• | Any broken valve springs |
• | Any excessive oil in combustion chambers or leaking valve seals |
• | A low cylinder compression |
• | Any incorrect basic engine parts. Inspect the following: |
Refer to
Symptoms - Engine Mechanical
in
Engine Mechanical-3.5L.
|
Additional Checks
|
• | Inspect the exhaust system for restrictions. Refer to
Restricted Exhaust
in Engine Exhaust. |
• | Inspect for any improper harness routing. An engine miss condition
can be caused by electromagnetic interference (EMI) on some engine controls
circuits. Use the scan tool to inspect for any erratic sensor values
or excessive changes in the indicated RPM with little change in the
actual engine RPM. This may indicate EMI is present. If a problem
exists, inspect for any improper routing of the harnesses near high
voltage components or high current components. |
• | Inspect the charging system. A bad diode in the alternator can
allow A/C noise to enter the electrical system. This may affect the engine
controls system operation. Refer to
Diagnostic Starting Point - Engine Electrical
in Engine Electrical. |
|