DEFINITION: Engine delivers less than expected power. Little or no increase in speed when accelerator pedal is pushed down part way.

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 18

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Visual/Physical Checks

1. Remove the air filter.
2. Inspect the air filter element.
3. Replace air filter element if necessary. Refer to Air Cleaner Element .

Was a repair required?

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Go to Step 18

Go to Step 5

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

Was a problem found?

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Go to Step 18

Go to Step 6

1. Check for water or alcohol contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 7

1. Using a scan tool, monitor KS system for spark retard activity.
2. If a problem is found, repair as necessary. Refer to Engine Knock Diagnosis in Engine General Information.

Was a problem found?

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Go to Step 18

Go to Step 8

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 18

Go to Step 9

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. Refer to On-Vehicle Service in Ignition System.

Notice: Determine the cause of the oil or gas fouled spark plugs in order to avoid damage to the new spark plugs.

Was a problem found?

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Go to Step 18

Go to Step 10

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

Was a problem found?

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Go to Step 18

Go to Step 11

1. Check PCM grounds for being clean, tight and in their 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 18

Go to Step 12

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 18

Go to Step 13

1. Check the Torque Converter Clutch (TCC) for proper operation. Refer to 4T60-E Transaxle Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 14

1. Refer to Engine Misfire Mechanical Diagnosis in Engine General Information to check for the following conditions:

•	Low compression.

•	Sticking or leaking valves.

•	Worn camshaft lobe(s).

•	Incorrect valve timing.

•	Bent push rods.

•	Worn rocker arms.

•	Broken valve springs.

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

Was a problem found?

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Go to Step 18

Go to Step 15

Is the vehicle equipped with a VIN 1 (RPO L67) engine?

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Go to Step 16

Go to Step 17

1. Check the boost control system. Refer to the Boost Control System Check .
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 18

Go to Step 17

1. Review all diagnostic procedures within this table.
2. When all procedures have been completed and no malfunctions are 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 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 18

Review technical bulletins

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

Is symptom still present?

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Go to Step 3

System OK