Leslie Simpson

running rough at 1000 to 1500 RPM, loss of power also.
Any suggestions people? its had new fuel filter and air filters, no fault codes.

43k with service history

ygmn

I would check for vacuum leaks, plugs and wires. - easy stuff first.

How do you know it does not throw code and have it stored?
IS it engine or maybe tranny?

Mud

Start with an OBD2 scantool that will at least give generic codes and real time run data, otherwise you're just guessing at parts. An ICarSoft V2 scanner for MB will also read all of the vehicle modules.
Even with the standard scantool, start by looking at what the O2 sensors and fuel trims are showing, plus MAF readings. If you've got a bad coil, that can show a misfire code but not always. However, a pending code may be stored. Throttle position sensor values can also be evaluated.
My point is to try to determine if the source is air/fuel or ignition related as a first pass. Those are the more common troubles.

TeeEl

My car does that when I cold start it. (In the morning or after a couple of days.) It chugs for 5-10 seconds then stabilizes. It's disconcerting. =(

Mud

TeeEl, that first cold start is when the engine is in open loop, running on a preset program. In a way it's running "blind" unless there is a major issue. As it warms it goes into closed loop, meaning that the various sensors are now taking over engine management. If there's a discrepancy, the closed loop operation is compensating for it.
Back again to using a scantool, it would interesting to look at run data in both open and closed loop.

TeeEl

Interesting bit of info, thank you. Still fully plan on picking up a scan tool, but for right now I'm saving my pennies for a trip overseas. Once that's done a scan tool is near the top of my "to get" list.