Backfires

DEFINITION
Fuel ignites in intake manifold, or in exhaust system, making a loud popping noise.

POWERTRAIN SYSTEM
Perform Powertrain System Check, if not already completed. Chart 1 Powertrain System Check

IGNITION SYSTEM
Perform Chart 1 Ignition System Check, looking in particular for:

^ Spark Plug Wires, crossfire between spark plug wires
- Crossfire between cylinders
- Wrong firing order

Chart 1 Ignition System Check

FUEL SYSTEM
Perform Chart 6C-1 Fuel System Check looking in particular for:

^ Fuel Quality
- Low Octane level
- Contaminants
^ Low Fuel Pressure
^ Low Flow Rate Injector

Chart 6C-1 Fuel System Check

EXHAUST DIAGNOSIS
Check exhaust system looking In particular for:

^ Restricted Catalytic Converter or Exhaust

MECHANICAL CAUSES
Check for the following mechanical causes:

- Valves Sticking in Guides
- Worn Camshaft Lobes
- Broken/Weak Valve Springs
- Camshaft Timing