Workshop Manual

6E–525
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Backfire Symptom
Step Action Value(s) Yes No
1 DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust
system, making a loud popping noise.
Was the “On-Board Diagnostic (OBD) System Check”
performed?
— Go to Step 2
Go to OBD
System
Check
2 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?
— Verify repair Go to Step 3
3 Was a visual/physical check performed?
— Go to Step 4
Go to Visual/
Physical
Check
4 1. Check for proper ignition voltage coil output with
spark tester J 26792 (ST-125). Refer to
Electric
Ignition System
for procedure.
2. If a problem is found, repair as necessary.
Was a problem found?
— Verify repair Go to Step 5
5 1. Remove spark plugs and check for wet plugs,
cracks, wear, improper gap, burned electrodes, or
heavy deposits. Refer to Electronic Ignition
System .
NOTE: If spark plugs are gas or oil fouled, the cause of
the fouling must be determined before replacing the
spark plugs. Refer to DTC P0172 to determine the
cause of a rich condition or Engine Mechanical for an oil
fouling condition.
2. If a problem is found, repair as necessary.
Was a problem found?
— Verify repair Go to Step 6
6 1. Visually/physically inspect the ignition coils for
cracks.
2. If a problem is found, repair as necessary.
Was a problem found?
— Verify repair Go to Step 7
7 1. Check for an intermittent ignition system
malfunction:
B Intermittent CKP 58X signal.
B Intermittent ignition feed circuit or sensor
ground circuit to the crankshaft position
sensor.
2. If a problem is found, repair as necessary.
Was a problem found?
— Verify repair Go to Step 8
8 1. Check the fuel pressure. Refer to Fuel System
Pressure Test .
2. If a problem is found, repair as necessary.
Was a problem found?
— Verify repair Go to Step 9