Not A Ford Question

[6T9PONY]

This doesn't have to do with my Mustang, or any other Ford....But I figure most everyone in here has a great amount of knowledge in all cars, not just Fords.

My girlfriend's '99 Cavalier Z24 (2.4L, Auto) has been running a little strange. Sometimes on acceleration the engine will stumble, sputter and pop a little bit with a LARGE amount of power loss. It sounds pretty horrible. It doesn't do it all the time, but it's not extremely rare, either.

It's a pretty loud noise, and the car shudders a little when it happens. It's very, very noticeable.

I'm probably not going to find out anything totally specific but I'd like to hear a few peoples' opinions on it then I'll take it from there....

Thanks in advance for all your help.