I happen to be having the identical problem as you wrote here in 2012:
"I noticed the same issue today as the OP. I was backing in my driveway with my trailer hooked up, and the engine started to tick a little, then started to really miss. The engine almost wanted to stall. I put it neutral, and gave it some rpm and it went away. Tried to back up again, and same issue. I figured out that if you push the brake, and give it a little gas, it will do the same thing. The engine sounds like a diesel. Engine runs fine, and revs up fine ones its in neutral. Any ideas?"
Wondering if you might let me know if you solved this problem? I'm taking my trailer out in a couple of days and this noise is driving me nuts.