Definition: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.

Did you perform the On-Board Diagnostic (OBD) System Check?

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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 present, correct the condition as instructed in the bulletin.

Did you find a bulletin that addresses the symptom?

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Go to Step 12

Go to Step 3

Did you perform a visual/physical check?

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Go to Step 4

Go to Symptoms

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

•	Clip the spark tester J 26792 to engine ground.

•	Connect one end of a spark plug wire to the spark tester J 26792 . Leave the other end of the spark plug wire connected to the coil being tested.

•	Disconnect the spark plug wire from the other spark plug on the same coil being tested, and ground the wire.

•	Crank the engine while observing the spark tester J 26792 . Look for a blue spark.

•	Repeat the above steps for each coil.

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

Was a problem found?

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Go to Step 12

Go to Step 5

1. Remove the spark plugs. Check for the spark plugs for the following conditions:

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Wet plugs

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Cracks

•	Excessive wear

•	An improper gap

•	Burned electrodes

•	Carbon tracking on the insulator

•	Heavy deposits. Refer to Ignition System Check

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

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

Was a problem found?

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Go to Step 12

Go to Step 6

Important: Spray the secondary ignition wires with a light mist of water in order to help locate an intermittent problem. The ignition components will arc to ground when a secondary component is malfunctioning. Refer to Ignition System Check

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

•	Check the ignition wires for cross firing.

•	Check the ignition wires arcing to ground.

•	Check the ignition wires for improper routing.

•	Check the ignition coils for cracks or for carbon tracking

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

Was a problem found?

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Go to Step 12

Go to Step 7

1. Check for an intermittent ignition system malfunction:

•	Check the primary connections at the ignition coil assembly.

•	Check for any intermittent connections at the Crankshaft Position sensor.

2. If a problem is present, repair as necessary. Refer to Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found?

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Go to Step 12

Go to Step 8

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

Was a problem found?

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Go to Step 12

Go to Step 9

1. Check for the following Engine Mechanical problems (Refer to Engine Mechanical ):

•	Low compression

•	Sticking valves

•	A hydraulic valve lifter problem

•	Leaking cylinder head gaskets

•	A worn or incorrect camshaft

•	Incorrect cam timing

•	A damaged timing belt

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

Was a problem found?

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Go to Step 12

Go to Step 10

1. Check the intake and the exhaust manifold(s) for casting flash. Refer to Engine Mechanical.
2. If a problem is present, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 11

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

•	The scan tool data

•	The Freeze Frame data

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

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

Was a problem found?

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Go to Step 12

Go to Step 3

Operate the vehicle under the same conditions (as closely as possible) as when the original symptom occurred.

Is the original symptom still present?

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Go to Step 3

Repair complete. If another driveability symptom exists, refer to Symptoms .