96 6.5TD Stumbles, hiccup and bucks

[johnpage]

I apologize in advance as I am new to this and the the truck belongs to my unlucky disabled brother who is stuck in an icy central Washington town trying to get home or xmas. He has no internet access. I'm trying to help and would appreciate any suggestions. I also thank you in advance!

His 6.5TD one ton 4X4 has started to buck while shortly after startup while driving. This happens especially when going down hill taking his foot off the throttle and when on flats when he takes his foot off to slow down or simply easing off the throttle. It really slams his drive line when this happens and he is worried that he will break something. He says it's like Bang Bang......Bang Bang Bang....and then he will apply the throttle and it will smooth out until he eases off again. It doesn't do it when accelerating or going up hill. Also when the engine is hot it is less of a problem.

Any ideas?
Thanks/John

[jpgreen]

I just found this, and I'm surprised no one has posted some help. Maybe everyone's gone for the holidays. I hope your brother makes it home, and have a Merry Christmas.


Read the stickies in this forum.

I would start by checking the battery cable connects, replacing the fuel filter and Oil Pressure Sending switch.* That switch controls the lower lift pump and when it starts going bad, you will get hesitations like a plugged filter. There are contacts in there that continually work and burn out. GM improved that part.

Then the famous 6.5 PMD. Get a remote mount PMD pronto. If this isn't causing part of the problem it soon will. I replaced mine with a 7 year warranty unit from USdiesel.