WHATS WRONG WITH MY 2000 FORD FOCUS SE???

[Mike]

ok i have a ford focus and it has recently had a rough ride it shakes and idles very slowly it sometimes stalls out but starts right back up i recently got all new hoses oil change and a cleaned my k and n air filter and it still rides rough. i got a new belt but not a timing belt? took it to a few mechanics and they diddent know whats wrong with it PLEASE HELP ME Its getting annoying. please if you know tell me what it could be and the price it would be to fix and the car has 137,000 miles on it