Robert A PRV engine is a clean burning engine when tuned properly. You should fly through the emissions check. The readings you gave us indicate a malfunction of a component. Also, an exhaust leak before the O2 sensor will usually cause a high HC reading. Unless the exhaust leak is massive it will probably not be enough to fail you but make it hard to do an accurate CO adjustment. Also, vacuum leaks can screw up all the readings depending on where they are (The bank with the exhaust leak, etc). Proper readings S/B CO .02 to .10, CO2 in the 15.0 area, HC 0 to 15 BTW the readings on my engine have been in this range for over 10 years and I have touched nothing except change the fuel accumulator, fuel filter, and air filter. That is over 35,000 miles ago. No brag, just fact. Since the car starts I would rule out spark for now. Make sure the Lambda system is working - the most obvious way to check it is to be sure the frequency valve is buzzing. I would suspect failure in the following order since you passed 12,000 miles ago - check fuse 7, replace the special Bosch relay for the frequency valve/lambda circuit (it is the only one like it in the DeLorean and it has to be that exact relay), the RPM relay, the O2 sensor, the frequency valve, or the cold start valve leaking. After all the correspondence to this point I am very suspicious of the Bosch relay or the RPM relay - Be sure fuse 7 is OK. Harold McElraft - 3354