i have a 94 grand prix and just changed a timing belt on it.it's the 3.4
dohc engine.problem now is it ran fine for about 10 minutes then upon it in
idling, i gave it some gas by way of pulling on the throttle under the hood
and there appeared to be a loud hiss from the front of engine then and
engine started to idle roughly,the cat also is making a lot of noise, like
it's all broken up inside,it wasn't this bad before belt went.but i had test
run the car several times adjusting timing belt aand it ran several times
with cams out of time,if the cat was going bad to begin with,could the
engine out of time running really destroyed it????just what are the signs of
a bad cat????what was the hiss then rough idle????is the cat bolted up to
where i can replacwe myself???