Restricted Catalytic Converter
A restricted catalytic converter can cause slow acceleration, lack of power at higher RPM, heat, or a sulfur smell.
Can I Drive?
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Most Likely Causes
- 1
Melted converter substrate
Misfires or rich running can overheat and melt the converter internally.
- 2
Broken substrate blocking exhaust
Loose pieces can restrict exhaust flow and reduce power.
- 3
Fuel or oil contamination
Oil burning, coolant burning, or rich mixtures can damage converter material.
How to Diagnose It
- 1
Check backpressure or vacuum behavior
Exhaust backpressure testing or vacuum drop at RPM can support restriction.
Tool: Backpressure gauge or vacuum gauge
- 2
Scan fuel trim and misfire history
Find the cause that may have damaged the converter.
Tool: Scan tool
- 3
Compare temperature and rattling clues
Hot spots or internal rattles can support converter damage but are not enough alone.
Tool: Infrared thermometer, listening check
How to Fix It
Repair misfire or rich-running cause first
Fix ignition, fuel, or oil-burning problems before replacing the converter.
Replace restricted converter when confirmed
Use a legal, vehicle-correct converter.
Verify exhaust flow after repair
Confirm power returns and codes do not reset.
Mistakes to Avoid
- Do not replace a catalytic converter before fixing the misfire or rich condition that damaged it.
- Do not remove or hollow out emissions equipment.
- Do not keep driving if power is falling and the converter is glowing or overheating.