Inspection/Tests
| 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 position.
|
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
|
| • | 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. |
|
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: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. | - | 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: |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. | - | 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 |
|
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.
|
Additional Inspections
|
| • | 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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