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
|
• | 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 incorrect RTV sealant. The sensors may have a
white , powdery coating and result in a high but false signal voltage rich exhaust
indication. The ECM will then reduce the amount of fuel delivered to the engine causing
a severe driveability problem. |
• | Inspect the mass air flow (MAF) sensor connections. Repair or replace
damaged terminals. Refer to
Connector Repairs . |
|
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 evaporative emission (EVAP) canister purge condition. |
- | An inaccurate MAF sensor. |
- | Vacuum hoses that are split, kinked, or incorrectly connected. |
- | An air intake duct that is collapsed or restricted. |
• | 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. Refer to
Exhaust Leakage . |
- | An inaccurate MAF sensor. |
- | Vacuum hoses that are split, kinked, or incorrectly 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 incorrect spark plug gap will cause a driveability problem. Gap the
spark plugs using a wire gage 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 ECM to operate in Engine Coolant Over Temperature-Fuel
Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the ECM
turns fuel OFF to four cylinders at a time to keep engine temperatures from
reaching damaging levels. The driver may perceive 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, refer to
Engine Overheating
for
diagnosis. |
• | Inspect for excessive crankshaft endplay that will cause the crankshaft
position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor.
Refer to
Crankshaft and Bearing Cleaning and Inspection . This could result in any of the
following conditions: |
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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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