This bulletin is being issued to revise the Rough, Unstable, or Incorrect
Idle and Stalling Diagnostic in the Engine Controls-6.6L sub-section of the
Service Manual. Please replace the current information in the Service Manual
with the following information.
The following information has been updated within SI. If you are using
a paper version of this Service Manual, please make a reference to this bulletin
on the affected page.
Inspection
| Action
|
DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle
may shake. Engine idle speed may vary in RPM. Either condition may be severe enough
to stall the engine.
|
Preliminary Inspection
|
| • | Refer to Important Preliminary Inspection Before Starting in Symptoms-Engine
Controls. |
| • | Compare the scan tool data at idle with the scan tool data list.
Refer to Scan Tool Data List. |
| • | Inspect the engine control module (ECM) grounds for being clean,
tight, and in the proper locations. |
| • | Remove and inspect the air filter element for dirt or for being
restricted. Refer to Air Cleaner Element Replacement. Replace as necessary. |
|
Fuel System Inspection
|
| • | Perform the fuel injector balance test. Refer to Fuel Injector
Balance Test with Tech 2. |
| • | Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis. |
| • | Inspect for a restriction in the fuel return system. Refer to
Fuel Return System Diagnosis. |
| • | Inspect for a contaminated fuel condition. Refer to Contaminants-in-Fuel
Diagnosis. |
| • | Inspect for a sticking Fuel Pressure Regulator. The symptom for
this condition will be an idle surge of at least 100 RPM. This surge
will be from 50 RPM above Desired Idle Speed to 50 RPM below
Desired Idle Speed. Refer to Fuel System Diagnosis-High Pressure Side. |
|
Sensor/System Inspection
|
| • | Inspect for proper crankcase ventilation. |
| • | Inspect for an intermittent crankshaft position (CKP) sensor signal
by monitoring the RPM with a scan tool. |
| • | Use a scan tool in order to monitor the sensor system for unusual
sensor readings. Refer to Scan Tool Data List. |
|
Engine Mechanical Inspection
|
| • | Inspect engine mechanical for the following: |
| - | Inspect the cylinder compression. Refer to Engine Compression
Test in Engine Mechanical 6.6L. |
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chamber--Leaking valve seals.
Refer to Oil Consumption Diagnosis in Engine Mechanical 6.6L. |
| • | Inspect the following components for incorrect basic engine parts: |
| - | Camshaft--Refer to Camshaft and Bearings Cleaning and Inspection
in Engine Mechanical. |
| - | Cylinder heads--Refer to Cylinder Head Cleaning and Inspection
in Engine Mechanical. |
| - | Pistons, connecting rods, or bearings--Refer to Piston, Connection
Rod, and Bearings Cleaning and Inspection in Engine Mechanical. |
|
Additional Inspection
|
| • | 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 |
| • | 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
indicates that EMI is present. If a problem exists,
inspect routing of high voltage components, such as fuel
injector wiring, near the sensor circuits. |
| • | Inspect the park neutral position (PNP) switch circuit. |
| • | Inspect for faulty motor mounts. Refer to Engine Mount Inspection
in Engine Mechanical 6.6L. |
| • | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
|
