Truck Repair: engine performance, air fuel ratio, fuel contamination

Question
I have a 3406 b model engine, which started losing power on my last trip.  I also noticed that the oil pressure decreases upon acceleration.  I stop and changed fuel filter which help for several hundered miles.  Then I had a oil change, with another fuel filter which had no effect.  Two weeks prior my fuel froze and I believe I might have water in the fuel.  Is it possible that the motor will miss and stutter because of water?

Answer
It sounds like you do have a fuel contamination problem.  I recommend running the tank low to get rid of the old fuel.  Refill at a place where you know the fuel is good.  Change the fuel filter and see if it gets better.  Did a change in the oil help the oil pressure?  If not, have the oil pressure checked with a manual gauge, then you can see if the reading on your truck matches.  If it does match, it may be time to roll in rods and mains and have the oil pump replaced.  If it doesn't match, and you have an electrical gauge, then change the sending unit.  After you have clean fuel and a new fuel filter and the low power is still a problem, have someone check your air fuel ratio valve.  You could have a blown diaphragm.  Hope this helps.