I can see a chain of events happening.
The exhaust leak, the hot air from the leak finally got bad enough to damage the spark plug wires.
The spark plug wires became damaged enough to ground to the engine so the plug stopped firing.
The plug stopped firing, and that unburnt fuel was sent out the exhaust system and was too much for the catalytic converter to deal with.
(that would have been the egg smell)
now the cat has melted into one solid glob and is clogging the exhaust system and the engine cant start (like sticking a potato up a tail pipe)
you can remove the oxygen sensor to let the exhaust gases escape. And try to start the car again.
Thursday, January 1st, 2009 AT 7:51 PM