Inspection
| Action
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DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down with no change in the accelerator pedal.
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Preliminary Inspection
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| • | Ensure the driver understands the torque converter clutch (TCC) operation. |
| • | Ensure the driver understands the A/C compressor operation. |
| • | Compare the scan tool data at idle with the scan tool data list. Refer to
Scan Tool Data List
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| • | Use the scan tool to ensure the vehicle speed sensor (VSS) reading matches the speedometer. This excludes vehicles with electronic transmissions where some variation between VSS and the speedometer is normal. |
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Sensor Inspection
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| • | Test for an intermittent FRP sensor signal by wiggling the harness between the sensor and the engine control module (ECM) with the ignition ON and the engine OFF, while monitoring the parameter with a scan tool. |
| • | Observe the Actual Fuel Rail Pressure and the Desired Fuel Rail Pressure parameters. If the pressure difference is more than 2 MPa, a fuel control issue may exist. |
| • | Inspect the crankshaft position (CKP) sensor reluctor wheel. Remove the CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose. |
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Fuel System Inspection
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| • | 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 Pressure Regulator Diagnosis
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Additional Inspection
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| • | Inspect the control module grounds for being clean, tight, and in their proper locations. |
| • | Inspect the generator output voltage. Repair if less than 9 volts or more than 16 volts. |
| • | Inspect the TCC operation. |
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