power and mpg loss

my 1997 4 cylinder has about 20,000 miles on a new engine.
has a good tune up, but all of a sudden it started losing power and the mpg went down to 20 mpg. as of now it just about will not take off.
i had a buick one time that did the same thing and it was the catalytic conveter. is it possible my geo has the same problem or is there another problem.
thanks :confused:

You might try and disconnect the exhaust pipe at the manifold and run it around the block. If power seems restored it could be your Cat.

You might try and disconnect the exhaust pipe at the manifold and run it around the block. If power seems restored it could be your Cat.
thanks , i will try that. think i will wait till cold weather is over. to cold to work on it now.