We've got a 1999 F250 that is well taken care of that we pull a horse trailer and flat bed with. Over the weekend we had a 7 hour drive with the horse trailer - about 3.5 hours into the drive the service engine light flashed and shortly after their was a loss of power. The loss of power would come and go for a few minutes while eventually a complete loss while going up a medium incline. I found a repair shop to pull into...they pulled codes that suggested problems with the exhaust. Changed the fuel filter, unplugged the bully dog and we were on our way again...20 miles down the road we were experiencing the same power loss. Shut off the truck for about 15 minutes and traveled the last couple hours not going over 55 without a problem. On the way home we made it about 5.5 out of the 7 hr trip before experiencing the same loss of power. Anytime we would hit even the slightest incline the truck would just fall flat on it's face.

The tech at the repair shopped suggested the bully dog chip had messed with the sensors in the truck.

Anyone deal with anything like this before? We take very good care of this truck, regular maintenance, spit shine and all.

Thank you in advance!

Editing to add:
It has been suggested that the exhaust temp could be too hot - but we have a 4" exhaust off the turbo to the back.

Also has been suggested with the bully dog tuner - we have been having too much soot build up.

Another suggestion was to check into our injectors, but two were just replaced last year.

We had the issue earlier this summer and the Ford dealership couldn't address to problem (came up during another longer length trip under heavy load).

Yet another suggestion was looking into sensors - but have been told 7.3's don't have sensors?

 

Welcome to the site..

What were the code/s retrieved?

Could certainly be a few reasons for the flat throttle, and the DTC's/CEL info would help with a direction.

But being it seems to run fine (?) until more of a higher throttle demand/grade and load,, one thing that gets overlooked quite often is the micro screens 'inside' the fuel tank built into fuel module. Not the large pick up screen on the nose of the module. The modules body snaps apart and the screens inside are removable/cleanable.. If the truck runs well (around town and unloaded ect) until there is a demand for more/heavier fuel drop, then I'd suspect the screens are restricting the flow/supply or other fuel delivery problems even fuel pump. Many a good pump had been replaced due to restricted screens tho.

A fuel pressure/volume test during a performance run would help the diagnosis, and could be other issues too, but if it feels like its running out of fuel, misfires/stumbles/rattles under hard acceleration then could be a restriction.

If you can duplicate the flat throttle 'each time' by pulling a long/steep grade, and during performance problem you then start to back out of the throttle 'slightly' and the engine quickly recovers and smooths, chances are it's the screens.

 

Thank you Hayapower! Greatly appreciated your insight and sounds sensible.

We did order a new fuel pump yesterday and will be checking the micro screens - thanks again!

 

When we do have the bully dog GT tuner plugged in, we still only get 15lbs of turbo boost...which is stock. Why don't we get more?

We appreciate you sharing your knowledge, we are in NW Wisconsin..no diesel motor heads up here ;-(