I have a 91 Mustang 5.0 installed in a kit car. It seems to run fine but the catalytic converters get red (literally) hot in under 3 minutes. I have checked the timing (10 degrees BTC), changed the distributor and mass air flow sensor. Any suggestions on where else to look?
Usually when the converter gets red hot like that it is because the engine is running too rich…too much unburned fuel and the converter is working its heart out to clean up the exhaust. What causes a rich condition:
1. Too much fuel pressure like from a bad fuel pressure regulator (sometimes the excess fuel fills up the crankcase as well…pull the oil dipstick and smell it)
2. Running bad, worn out spark plugs, plug wires, distributor cap and rotor
3. Vacuum leak under the hood – check all rubber vacuum lines and connections
4. Ignition timing out of control – bad ignition module
bad oxygen sensor
5. Restriction in the exhaust system – converter or muffler is stopped up with carbon