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 Powertrain 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 Check

Be sure driver understands Transaxle torque converter clutch and A/C compressor operation as explained in the owners 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. Check Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensors (HO2S) should respond quickly to different throttle position. If they don't, check the HO2S for silicon or other contaminants from fuel or use of improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S 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 to Powertrain Control Module (PCM) and Sensors.
2. If a problem is found, repair as necessary.

Was a repair required?

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Go to Step 22

Go to Step 6

1. Check fuel pressure. Fuel System 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 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 Diagnostic Support page of DTC P0172.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 22

Go to Step 10

1. Check items that can cause the engine to run lean. Refer to Diagnostic Aids of DTC P0171.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 22

Go to Step 10

1. Check for proper ignition coil output voltage with spark tester J 26792 (ST 125):

•	Clip the spark tester J 26792 to engine ground.

•	Connect J 26792 to an ignition wire then ground spark plug end of ignition wire from companion cylinder. The companion cylinder is the cylinder that shares the same ignition coil.

•	Crank the engine while observing the spark tester J 26792; a crisp blue spark should be observed.

•	Repeat the above steps for each coil.

2. If adequate spark is not present at all coils, repair as necessary.

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 Electronic Ignition System.
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. Refer to Electronic Ignition System.

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 imp

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

Was a problem found?

30 K ohms (30,000 ohms)

Go to Step 22

Go to Step 13

1. Check 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 22

Go to Step 14

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

Did any coil(s) require replacement?

5K-7 K ohms (5000-7000 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 spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Refer to Electronic Ignition System.
2. 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 PCM wiring diagrams in Electrical Diagnosis section 8A.
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 Electrical Diagnosis Section 8A for wiring repair procedures.

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 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 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.

•	Scan Tool data.

•	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 Service 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

Repair complete