Jerking Jetta!!!!

I have a 94 diesel 1.9 Jetta.(only sold in Canada) and it sometimes starts jerking. Sometimes at idle and sometimes when I'm going fast, but vary inconsistently. One day it would run horrible and the next fine. And when it jerks its scary, like shutting the key off for a second scary. It is always in little short bursts, and always keeps running, then it stoped working and I needed to get a tow home. Now the car will start, and idle but there is no power to get me moving fast enough to drive on the road (just around my driveway) or it will start jerking again.
This car has been a nightmare since I got it a year ago I put $4000 into it in parts, my labor. Everything has been replaced except the injection pump. Can you ajust them? Help Steve

Don't try to adjust the injection pump! At least don't try to adjust the flow.
I'd check the timing before anything else. Make sure all your timing marks are correct, then check the timing on the pump. You loosen 3 (?) bolts that allow the pump to rotate then adjust the timing. It's been a few years since I've worked on a diesel, but I think they describe it in one of the autoparts store manuals. The Haynes doesn't do the diesel. I can't remember the name of the manual that does, but it's one other very common ones.
Did your replace the fuel filter? Have you checked the fuel lines? Air may be getting sucked in. The pump pulls the fuel all the way from the tank and there is a lot of fuel line in between. Did you have the lines bled properly when the other work was done?

Thank you for the quick response Doug, but I fixed the problem. On the fuel injection pump there is the shut off sensor for the engine. The connection to that sensor was loose and it was rattling around and making the chugging. The connection is a crappy little push on metal clip that is easy to corrode and easy to break. That was it. But I did something that you said not too. I touched the fuel adjustment screw. So can you are somebody please tell me how to adjust the fuel mix. I read that, if it is not adjusted properly it can fry my turbo. Thanks in advance.