i had the same thing happen on my 240....it was my 3rd fuel injector.....but i started out just pulling out spark plugs...pulled em til i got to cylinder 3...with all the other plugged in the 3rd cylinder wasnt making a diffrence....replaced the plugs same shit so i replaced the 3rd fuel injector.....runs great now.....check yours out or if u want pm me and i will give u my number or whatever and take a look at it for you....peace