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.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

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Go to

Powertrain On Board Diagnostic (OBD) System Check

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

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Go to Step 3

Was visual/physical check performed?

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Go to

Important Preliminary Checks

1. Check the Oxygen Sensor (O2S 1). The Oxygen Sensor (O2S 1) should respond quickly to different throttle position.
2. If the O2S 1 doesn't respond quickly, check the O2S 1 for silicon or other contaminants from fuel or use of improper RTV sealant. The sensor may have a white powdery coating. Silicon contamination causes in a high but false O2S 1 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 Powertrain Control Module Inputs Diagnosis .
3. If a problem is found, repair as necessary.

Was a repair required?

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Go to Step 5

1. Check the fuel pressure. Refer to Fuel System Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 6

Monitor the Long Term Fuel Trim on the scan tool.

Is the Long Term Fuel Trim significantly in the negative range (Rich condition)?

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Go to Step 8

1. Check the items that can cause the engine to run rich. Refer to DTC P0172 Fuel Trim System Rich .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

1. Check the items that can cause the engine to run lean. Refer to DTC P0171 Fuel Trim System Lean .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

1. Check for proper ignition voltage output with spark plug jumper wires J 36012 and spark tester J  26792.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 10

1. Check the ignition coils for cracks or carbon tracking.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 11

1. Check the ignition coil secondary resistance.
2. Replace any coil(s) which are not within the specified values.

Did any coil(s) require replacement?

5000-8000 ohms (5 Kohms-8 ohms)

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Go to Step 12

Notice: If spark plugs are gas or oil fouled, determime the cause of the fouling before replacing the spark plugs in order to avoid damage to the new spark plugs.

1. Remove the spark plugs.
2. Check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
3. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 13

1. Check the injector connections.
2. If any of the injectors connectors are connected to an incorrect cylinder, correct as necessary.

Was a problem found?

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Go to Step 14

1. Check the PCM grounds for being clean, tight and in the proper locations. Refer to PCM wiring diagrams in Section 8A.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 15

1. Visually/physically check vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 16

1. Check for proper generator voltage output.
2. The voltage should be between the specified values.

Is the voltage between the specified values?

11-16V

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Go to Section 6D

1. Review all diagnostic procedures within this table.
2. If all procedures have been completed and no malfunctions have been found, review/inspect the following items:

•	Visual/physical inspection.

•	Scan tool data.

•	All electrical connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

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Check for Service Bulletins

Operate vehicle within the conditions under which the original symptom was noted.

Does the system now operate properly?

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System OK

Go to Step 2