I have a 1994 850 with 330K on it. My brother noticed what he thought was a lower-engine noise that he thought might be the rings on number 2. I drove the car and noticed very, very low power. Drove 60k on it and the exhaust (catalytic got so hot that the insulation on the firewall was burned and one of the gas lines was melted!). I spent four hours yesterday replacing the gas line outside the muffler shop (they wouldn't look at it with the gas leak). They look at the catalytic this moring and advised me that it's not plugged. I have since asked that they re-attach the pipe. What else could it be? Symptoms include rough start (bareley holding an idle), then starts idling smooth. NO POWER and slow from a stop. Takes a long time ot get to highway speed. So hot that the floorgets hot. Any ideas would be welcome - O2 sensor? Other?

 

You have a misfire, most likely. It's causing excess gas to go into the catalytic converter, which burns it off. If it's not plugged yet, it will be soon if you keep driving it. You need to diagnose the miss. With that kind of mileage, my first step would be to do a compression check. If that checks out, then change the plugs, cap, and rotor, and test the wires with a ohmmeter- should be less than 5,000 ohms per foot of wire. Replace them if they're more than that. If you still have a problem, start looking to a fuel system problem. Good luck!