Re: 156 Mystery Misfire?
Your P0430 is most likely a result of the misfire.
This code is detected and set by the ECU evaluating the output of the pre and post catalytic converter oxygen sensor output voltages, usually during a decent run. If the cat doesn't clean enough of the pollutants contained in the exhaust gas, the code sets. If you clear this fault it will normally take a fair bit of driving before it returns.
This code is typically solved by resloving the root cause of the misfire, and then replacing the catalytic converter(s) - ouch. If you replace the catalytic converter (which may stop this code appearing) prior to fixing the misfire, the new cat(s) will be damaged again.
On the modern motor vehicle (with a catalytic converter emission control device) driving with a misfire will eventually kill the cat due to unburnt fuel raising the temperature of the cat to a point where it disintegrates. Some engine management systems stop the fuel injecting on the misfiring cylinder sa as to protect the cat(s).
You need to get to why the misfire, then replace the cat(s).
Typical causes for misifres are a lack of fuel (injection system), too much fuel (injection system) , a lack of spark (ignition system), too much air (leaking manifold - lean misfire), lack of compression (sticking valves).
You need to get the car put on an oscilloscope and graphing scan tool to thoroughly check the engine management system.
Hope this helps?