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

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 11

Go to Step 3

Was visual/physical check performed?

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Go to Step 4

Go to

Important Preliminary Checks

1. Check for proper ignition coil output voltage with the spark plug jumper wires J 36012 and the spark tester J 26792.
2. If a problem is found, repair as necessary.

Was a problem found?

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Go to Step 11

Go to Step 5

1. Remove the spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.

Notice: If spark plugs are gas or oil fouled, determime the cause of the fouling before replacing the 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 11

Go to Step 6

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

Was a problem found?

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Go to Step 11

Go to Step 7

1. Perform the Fuel Injector Solenoid Coil Test (ECT Within 10C-35C (50F-95F) and Fuel Injector Balance Test .
2. Replace any injector malfunctioning.

Were any injector(s) replaced?

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Go to Step 11

Go to Step 8

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 11

Go to Step 9

1. Check the 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 11

Go to Step 10

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 items:

•	Visual/physical inspection.

•	Scan tool 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 11

Check for Service Bulletins

Operate vehicle within the conditions under which the original symptom was noted.

Does the system now operate properly?

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System OK

Go to Step 2