Land Rover Repair: 1996 Range Rover exhaust, temp gauge, faulty sensor

Question
I have a 1996 Range Rover, and I took it in to a local mechanic (not the dealer) when the check engine light came on.  He said it read code P1138, but couldn't offer much help.  There is an oil leak somewhere, the exhaust smells like turpentine, and the motor runs rough when idling.  The temperature gauge does not move off "C" either.  Also, when I was driving on the highway, after about 50 miles the A/C suddenly blew extremely hot on the passenger side but not on the driver's side.  I read on another post that this could be the catalytic converter - could I possibly route around the faulty sensor?  If so, where do I get parts?  Thanks...

Answer
P1138 usually means one side of the engine is running rich.  We have routines to test this in our diagnostic system.  That's your next step.

If the temp gauge is stuck on C either the gauge is faulty or the thermostat is stuck open.  A stuck thermostat might cause the rich running problem.  Check and correct that situation.

Hot air on the passenger side and cool air on the driver side is an indication that the distribution door motors in your climate control are going bad - a $1000 repair or 8 hours of DIY work.

None of these issues have anything to do with your catalytic converter