OVERHEATED, MELTED OR BROKEN CONVERTERS
Any malfunction causing an unusually high level of HC or CO (in conjunction with high levels of O2) to enter the converter, will dramatically elevate its temperature.
Potential causes for high HC readings may include:
AFR Cylinder imbalance
Excessive engine or vehicle load
- Fuel delivery system or fuel quality
- Sluggish (worn out) O2 sensors
- Excessive backpressure
- Low compression
Poor spark, or weak ignition
NOTE: Temperatures in excess of 1600º F may damage catalyst, without visible signs of melting
COATED / OIL-FOULED SUBSTRATE
Catalyst poisoning occurs when the converter is exposed to emissions containing substances that coat the working surfaces, enveloping the catalyst to the point it cannot contact - and treat - the exhaust.
Potential causes for coated or fouled substrate may include:
Excessive carbon build-up in exhaust
Internal coolant leaks (head / intake gasket)
Use of non-converter-safe gasket sealants
Excessive oil consumption (burning oil)
Improper fuels or additives (E85, diesel)
The primary cause of structural damage is road debris striking the converter. Normally, some evidence of impact is visible on the converter shield.
Other conditions that may cause structural damage: