Backfire Symptom
DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
BACKFIRE SYMPTOM
| Step |
Action |
Values |
Yes |
No |
| 1 |
Was the "On-Board Diagnostic (OBDII) System Check" performed? |
- |
Go to Step 2 |
Go to On-Board Diagnostic (OBD-II) System Check |
| 2 |
- Perform a bulletin search.
- 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 |
- Check for proper ignition voltage coil output with spark tester J 26792 (ST -125). Refer to IGNITION SYSTEM
for procedure.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 5 |
| 5 |
- Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Refer to 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
, P0175
to determine the cause of a rich condition or Engine Mechanical for an oil fouling condition.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 6 |
| 6 |
- Visually/physically inspect the ignition coils for cracks.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 7 |
| 7 |
- Check for an intermittent ignition system malfunction:
- Intermittent CKP 58X signal.
- Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor.
- Camshaft damaged
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 8 |
| 8 |
- Check the fuel pressure. Refer to Fuel System Check (High Pressure Line)
or Fuel System Check (Low Pressure Line)
.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 9 |
| 9 |
- Check for the following engine mechanical conditions. Refer to ENGINE MECHANICAL (6VE1-DI - 3.5L)
for diagnosis procedures:
- Low compression
- Sticking or leaking valves
- Worn camshaft lobes
- Camshaft drive belt slipped or stripped
- Incorrect valve timing
- If a problem is found, repair as necessary.
Was a problem found? |
--- |
Verify repair |
Go to Step 10 |
| 10 |
- Check the intake and exhaust manifold(s) for casting flash. Refer to ENGINE MECHANICAL (6VE1-DI - 3.5L)
.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
Go to Step 11 |
| 11 |
- Review all diagnostic procedures within this table.
- If all procedures have been completed and no malfunctions have been found, review/inspect the following:
- Visual/physical inspection
- Tech 2 data
- Freeze Frame data/Failure Records butter
- All electrical connections within a suspected circuit and/or system.
- If a problem is found, repair as necessary.
Was a problem found? |
- |
Verify repair |
- |