I have a 2000 volvo s40 112K. When i rev the engine between 2000-3000 rpm the engine runs rough and I can feel a vibratin. I have changed the engine mounts, but problem still exists. It idles fine and after 3000 rpm it smooths out. Any idea's on what may be the problem??

 

my 2004.5 is kind of doing the same thing now, last night i heard a loud pop and then that started, guy at autozone said it was probably the muffler or the catalytic converter. I put some fuel injection cleaner in it and it seems to be okay and may be getting better but i have to do some more research to see exactly what is wrong if anything. I hope your problem gets solved as well!