Engine bucking

I have a 2002 Dodge Intrepid SE (2.7L V6) with just under 66,000 miles on it. For the past 6 months the check engine light would come on, sometimes for days, then go off for days or weeks. I took it in to the dealership once, but the light would not come on. Recently, it has also taken to bucking. When the RPMs get a little above 2000 and accelerating (even mildly), the car jerks violently and loses speed. I know this has happened to other people because a man (who owned a 2002 intrepid and noticed mine) asked me if my car was behaving that way sometimes. At that time I did not have any such problems. This is becoming a safety hazard. It doesn't seem to switch into this mode unless starting the car or trying to pull out from idle, such as on a metered on-ramp. Most times, turning the engine off and restarting fixes the bucking problem, but the check engine light will stay on. It never bucks without the check engine light being on, but the check engine light can be on without it performing its wild bronco act. While in the bucking mode, I can accelerate as fast as I want so long as I keep the RPMs below 2000. I can also get above 2000 by going downhill and it seems okay to maintain at that engine speed. The problem is still intermittant. It can go for days without this happening. I need something to discuss with the service manager at the dealer. If you have heard of this type of problem with the Intrepid, please let me know wherein lies the problem.
Thank You