Possible Causes

Possible causes are:

• Damaged catalytic converter.
• Damaged exhaust manifold.
• Damaged exhaust system pipe.
• Damaged HO2S.
• Damaged muffler/tailpipe assembly.
• Downstream HO2S wires improperly connected.
• Engine misfire.
• Fuel pressure too high.
• Malfunctioning ECT/CHT sensor.
• Oil contamination.
• Retarded spark timing.
• Using leaded fuel.