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

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 12

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to Visual/Physical Checks

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

-	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, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 5

1. Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Refer to Electronic Ignition System.

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 found, repair as necessary.

Was a problem found?

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Go to Step 12

Go to Step 6

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

•	Ignition wires for cross firing.

•	Ignition wires arcing to ground.

•	Ignition wires for improper routing.

•	Ignition coils for cracks or carbon tracking

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. If a problem is found, 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:

•	Intermittent 7X CKP or CKP 24X signal.

•	Intermittent sensor feed circuit or sensor ground circuit to the crankshaft position sensor or camshaft position sensors

•	Intermittent 3X reference signal.

•	Intermittent Camshaft position signal.

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

Was a problem found?

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Go to Step 12

Go to Step 8

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 12

Go to Step 9

1. Check engine mechanical for the following conditions. Refer to Engine Mechanical for diagnosis procedures.

•	Low compression.

•	Sticking or leaking valves.

•	Worn camshaft lobe(s).

•	Incorrect valve timing.

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

Was a problem found?

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Go to Step 12

Go to Step 10

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

Was a problem found?

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Go to Step 12

Go to Step 11

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 12

Refer to 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

System OK