1996 - 6.5 - sporadic power loss and surging while driving

[PJPDsurf]

I am looking for some help in trying to identify why my 6.5 is having the following issues:

1) While driving on uphill grades it sometimes has a surging effect where power is being lost (seems related to point 2 below);
2) I lost most power like it is sucking wind on 3 road trips after 1-2 hours of driving - this seems to fix itself after letting it sit for a day or 2.

There are no check engine lights. I had the IP replaced about 4 months ago. My mechanic can't find anything and it only seems to happen on longer road trips so it is impossible for him to reproduce.

Thoughts?

[xtrempickup]

check fuel filter and lift pump first then can go from there to other possibilities

[bsevans]

I had a similar problem that turned out to be the accelerator. One of the encoders went out. The dealership replaced the assembly and all was well.

[JohnC]

Have you checked to see if the fuel cap is venting properly?