Checks
| Action
|
DEFINITION: Engine power variation under steady throttle
or cruise. Feels like the vehicle speeds up and slows down with no change
in the accelerator pedal.
|
Preliminary
|
| • | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
Be sure that the driver understands the transmission torque converter
clutch (TCC), and A/C compressor operation as explained in the owners manual.
Inform the customer how the TCC and the A/C system operate.
|
Sensor/System
|
| • | Check the HO2 sensors. The HO2 sensors should respond quickly
to different throttle positions. If they do not, check the HO2 sensor for
the following conditions: |
| - | Contaminants from the fuel. |
| - | The sensors may have a white powdery coating. This will result in a
high but false signal voltage (rich exhaust indicated). The PCM will reduce
the amount of fuel delivered to the engine causing a severe driveability
condition. |
| • | Check the MAF sensor and intake air system for proper connections. |
| • | Check the EGR system for proper operation. |
|
Fuel System
|
| • | Check for conditions which can cause an engine to run rich and/or
lean. |
|
Ignition System
|
| • | Check for proper ignition voltage output using the J 26792
spark tester. Refer to Secondary Ignition
System Diagnosis. |
| • | Check for damaged ignition coils within the ignition coil module
assemblies. |
| • | Check for damaged or misaligned spark plug boots. |
| • | Check for a missing or damaged ignition module ground spring. |
| | Important: If the spark plugs are gas or oil fouled, the cause of the fouling must
be determined before replacing the spark plugs.
|
| • | Check the spark plugs for the following conditions: |
| | Important: An improper spark plug gap will cause a driveability condition. The
spark plug gapping should be done using a wire gauge gap tool (J 413319).
|
| - | Wrong heat range or improper reach |
| - | Burned or damaged electrodes |
|
Additional Checks
|
| • | Visually/Physically inspect the vacuum hoses for splits, kinks,
and improper connections or routing. Refer to the Vehicle Emission Control
Information label. |
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