Checks
| Action
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DEFINITION: The engine power output varies under a steady throttle or cruise. The vehicle seems to speed up and slow down with no change in the accelerator pedal position.
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Preliminary Checks
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| • | Educate the driver about normal A/C compressor operation. |
| • | Use a scan tool in order to verfy that the reading of VSS matches the reading of the vehicle speedometer. |
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Sensor Check
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| • | Check the performance of the heated oxygen sensor (HO2S) sensor 1 and the HO2S 2. Refer to Diagnostic Aids in DTC P0131 through DTC P0141. |
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Fuel System Checks
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| • | Determine whether a rich or lean fueling condition can cause the concern. Drive the vehicle at the speed of the concern. Monitor the Fuel Trim parameters on a scan tool in order to identify the fuel system status. |
| • | Check the fuel injector for a conical spray pattern and even flow. |
| • | Check that the fuel injector electrical resistance is 0.5-1.5 ohms at 20°C (68°F). |
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Ignition System Checks
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| • | Check for the proper secondary voltage output with a
J 26792 spark tester or an equivalent. |
| • | Check the spark plugs for any of the following conditions: |
| - | Wet (fuel fouled) plugs. |
| - | A terminal screw that is bent or loose (rotate and pull). |
| - | A ceramic insulator that has cracks, carbon tracking or deposits (red or black dust) |
| - | A tip insulator that has cracks, carbon tracking, deposits (oil, carbon, glazing, fuel additive), or is loose (rattles). |
| - | A center electrode that is loose (wiggles side to side) |
| - | An incorrect spark plug gap that is too wide or too narrow. |
| - | Platinum pads that are missing. |
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Additional Checks
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| • | Check the PCM grounds for being clean, tight, and in the proper location. Refer to
PCM Power and Ground
. |
| • | Check the generator output voltage. |
| • | Check the vacuum lines and hoses for leaks or restrictions. Refer to the Vehicle Emission Control Information label for the correct routing of vacuum lines. |
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