'93 2.5l mileage problem

Howdy all. The problem I'm haveing started literaly over night. I was getting around 23 mpg and now its getting like 10 mpg. What could of happened? I cecked my codes and the o2 sensor is bad but, that couldn't effect the mpg that bad, could it?! Also, I got a code for the pcm has resantly been disconneted, but it hasn't, whats up with that? Also with the mpg, I'm a sensable drive and the tires are aired properly and no break are hanging up.
The engine has 160,000 or so and I was wondering could the cat converter be pluged? Well any help would be great!
Thanks

if your using that much gas you should be able to smell it. and it should like shit....ne more info...

Actually yes, while driving I can smell fuel but, I've looked all around the fuel tank and the lines also around the engine and I can't see anywhere that may be leaking.

can you take it somewhere and have them put it on a lift? then you should find it...or light a match...lol...