Engine surging at above 2000 rpm

[kirkmc]

I have a 2008 CNH TD 5050 that starting surging while balling hay. Never had any problem with the engine prior to this. It idles fine and seems to be OK until the
tach gets to over 2000 rpm. At that point, white smoke starts coming out of the stack pipe and the engine slows down to around 1500 rpm and will not go higher. I
can cut the engine off and wait a minute to crank it and it will go back to full throtttle before starting the process over again. Really sounded like a fuel
restriction issue so I replaced the lift pump which I had had to do a couple of times before. This didn't fix it so I blew through the fuel line back into the
tank to clear any obstructions. That didn't fix it so I took the tank off and cleaned it out. Ther was very little debris in it and nothing stopping the lines. I
have changed the fuel filter but still no success. It still revs up as it should but within a couple of minutes starts blowing a little white smoke, starts
missing and then self idles to around 1500 rpm and won't go higher until it is shut off and restarted. I hope some of you can see what I can't and have an idea as
to what is going on.The way it strted and the symptoms make me think it is not a major isuue but obviuosly beyound me. Thanks for any suggestions.

 

[Majorman]

Does it have an emission control system? Sounds like diesel cars I have had when the EGR valve gets clogged with carbon.

 

[kirkmc]

It doesn't require DEF and i'm really not sure. Good thought. Thanks. i'll check with the dealership to ask. unfortuantely I don't have a dealership near me so I have to try to solve everything myself.