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 Step 2

Go to the 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 22

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Visual/Physical Checks .

Be sure driver understands Transaxle torque converter clutch and A/C compressor operation as explained in the owner's manual Inform customer how TCC and the A/C clutch operates

Is the customer experiencing a normal condition?

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System OK

Go to Step 5

1. Start the engine.
2. Observe the HO2S 1 voltage display on the scan tool while modulating the throttle.
3. If the HO2S 1 voltage does not respond quickly to changes in throttle position, check for a contaminated HO2S. Refer to

   Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

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Was a problem found?

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Go to Step 22

Go to Step 6

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

Was a problem found?

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Go to Step 22

Go to Step 7

Monitor Long Term Fuel Trim on the scan tool.

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

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Go to Step 8

Go to Step 9

1. Check items that can cause the engine to run rich. Refer to Diagnostic Aids in 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 10

Go to Step 22

1. Check items that can cause the engine to run lean. Refer to Diagnostic Aids in 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 10

Go to Step 22

1. Check for proper ignition coil output voltage with a J 26792 spark tester:

•	Clip the spark tester to engine ground.

•	Connect one end of a spark plug wire to the spark tester; connect the other end of the spark plug wire to the coil being tested.

•	Connect one end of another spark plug wire to the other coil tower; connect the other end of the spark plug wire to ground.

•	Crank the engine while observing the spark tester; a crisp blue spark should be observed.

•	Repeat the above steps for each coil.

2. If adequate spark is not present at all coils, replace coil(s) as necessary. Refer to Ignition Control Module Replacement .

Was a problem found?

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Go to Step 22

Go to Step 11

1. Check for loose ignition control module ground. Refer to Ground Distribution in Electrical Diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 22

Go to Step 12

Important: Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem Ignition components will arc to ground when a secondary component is faulty.

1. Visually/Physically inspect secondary ignition wires. Check for the following conditions:

•	Check all ignition wire resistances; should be less than the specified value.

•	Ignition wires for cross firing.

•	Ignition wires arcing to ground.

•	Ignition wires for improper routing.

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

Was a problem found?

30,000 ohms (30K ohms)

Go to Step 22

Go to Step 13

1. Inspect the ignition coils for cracks or carbon tracking.
2. If a problem is found, replace coil(s) as necessary. Refer to Ignition Control Module Replacement .

Was a problem found?

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Go to Step 22

Go to Step 14

1. Check ignition coil secondary resistance.
2. Replace any coil(s) which are not within the specified resistance values. Refer to Ignition Control Module Replacement .

Was a problem found?

5000 - 8000 ohms

(5-8K ohms)

Go to Step 22

Go to Step 15

Notice: Determine the cause of the oil or gas fouled 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 22

Go to Step 16

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

Was a problem found?

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Go to Step 22

Go to Step 17

1. Check PCM grounds for being clean, tight and in the proper locations. Refer to Ground Distribution in Electrical Diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 22

Go to Step 18

1. Check MAF sensor connections.
2. If a problem is found, replace faulty terminals as necessary. Refer to Wiring Repair in Electrical Diagnosis.

Was a problem found?

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Go to Step 22

Go to Step 19

1. Visually/physically check vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label.

•	All with VIN 1 (RPO L67) except Bonneville - Refer to C/H-Car with VIN 1

•	Bonneville with VIN 1 (RPO L67) - Refer to Pontiac H-Car with VIN 1

•	C-Car with VIN K (RPO L36) - Refer to C-Car with VIN K

•	H-Car with VIN K (RPO L36) - Refer to H-Car with VIN K

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

Was a problem found?

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Go to Step 22

Go to Step 20

1. Check exhaust system for possible restriction:

•	Inspect exhaust system for damaged or collapsed pipes.

•	Inspect muffler for heat distress or possible internal failure.

•	Check for a possible plugged three-way catalytic converter by checking exhaust system back pressure. Refer to Restricted Exhaust System Check .

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

Was a problem found?

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Go to Step 22

Go to Step 21

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:

•	Visual/physical inspection. Refer to Visual/Physical Checks .

•	Scan tool data. Refer to Engine Scan Tool Data List .

•	Freeze Frame data/Failure Records 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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Go to Step 22

Review technical bulletins

Operate the vehicle to duplicate conditions present when the original symptom was noted.

Is symptom still present?

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Go to Step 3

System OK