Inspection/Tests
| Action
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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 position.
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Preliminary
|
| • | Inspect the powertrain control module (PCM) grounds for being clean, tight,
and in the proper locations. |
| • | Verify the driver understands the operation of 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 clutch operates. |
|
Sensor/System
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| • | Inspect the heated oxygen sensors (HO2S). The HO2S should respond quickly
to different throttle positions. If they do not, inspect the HO2S for silicon or other
contaminates from fuel or the use of improper RTV sealant. The sensors may have a
white , powdery coating and result in a high but false signal voltage rich exhaust
indication. The PCM will then reduce the amount of fuel delivered to the engine causing
a severe driveability problem. For more information, refer to
Oil Consumption Diagnosis in
Engine Mechanical. |
| • | Inspect the mass air flow (MAF) sensor connections. Repair or replace
damaged terminals. Refer to
Connector Repairs in Wiring Systems. |
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Fuel System
|
| • | Verify that each injector harness is connected to the correct injector
or cylinder. Relocate injector harnesses as necessary. |
| • | Inspect for the following that may cause the engine to run rich: |
| - | Water intrusion in the HO2S connector |
| - | Engine oil contaminated by fuel |
| - | An EVAP canister purge condition |
| - | An inaccurate mass air flow (MAF) sensor |
| - | Vacuum hoses that are split, kinked, or improperly connected |
| • | Inspect for the following conditions that may cause the engine to run
lean: |
| - | Water intrusion in the HO2S connector |
| - | An exhaust leak between the HO2S and the engine. |
| - | An inaccurate MAF sensor |
| - | Vacuum hoses that are split, kinked, or improperly connected |
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Ignition System
|
| • | Soak the secondary ignition system with water from a spray bottle. Soaking
the secondary ignition system may help locate damaged or deteriorated components.
Look and listen for arcing or misfiring as you apply the water. |
| • | Remove the spark plugs and inspect for the following: |
Refer to
Spark Plug Inspection.
| • | An improper spark plug gap will cause a driveability problem. Gap the
spark plugs using a wire gauge gap tool. Refer to
Spark Plug Replacement. |
| • | Determine the cause of the fouling before replacing the spark plugs. |
| • | Monitor the Misfire Current Counters while driving the vehicle within
the conditions that the misfire occurred. If a misfiring cylinder can be located,
use the DTC P0300 table for diagnosis. Refer to
DTC P0300. |
|
Engine Mechanical
| Verify that the engine coolant temperature (ECT) is not above 130°C (266°F).
This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel
Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the PCM
turns fuel OFF to four cylinders at a time to keep engine temperatures from reaching
damaging levels. The system perceives Engine Coolant Over Temperature-Fuel
Disabled Mode as a lack of power, miss, or rough idle. If the vehicle operates in
Engine Coolant Over Temperature-Fuel Disabled Mode.
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Additional Inspections
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| • | Visually and physically inspect vacuum hoses for splits, kinks, and proper
connections and routing as shown on the Vehicle Emission Control Information label. |
| • | Inspect the transmission torque converter clutch (TCC) operation. A TCC
applying too soon can cause the engine to spark knock. |
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