Not sure if this is correct forum but will start here 1997 F250HD 7.3 powerstroke, E40D transmission, have had an intermittent issue for some while (5 years off and on) during traffic the truck is jerky like it may not be shifting correctly (upshift downshift, upshift downshift), over the years it has become more and more of an issue. Replaced VSS but to no avail, just rebuilt transmission and still it happens. Just finished a 1000 round trip and have more info. if the cruise control is on the truck moves and travels very smoothly, shift is smooth and timely, but as soon as I disengage the cruise control and and go back to manual acc control the truck has issues, definitely affecting the transmission shifting, I thought it might be injector related, but if so I would expect similar issues with cruise on as well as off, and some kind of error code logged. , as soon as I can get to a place to reengage the cruise the truck runs issue free, this happens at a variety of speeds, no codes are thrown and during a scan a P1111 is only code, which the charts indicates all is well. The valley has been rebuilt, both tanks replaced (they developed leaks), transmission replaced, all fluids oil, water rear end oil, etc are all flushed and replaced.. Had someone suggest I look at the accelerator control circuitry, is this this electronic control on this truck, does anyone know. Looking for suggestions, multiple mechanics, including Ford mechanics, have been unable to pinpoint a cause or even if it is engine or transmission related. Looking for any help or suggestions to assist in identifying the issue. Thanks

 

You mentioned the VSS, but did you replace the TPS?

 

No but it is next as sson as I find one

 

make sure you are not using LEDs in rear tail lights and make sure the third is working

with out the right resistance of regular bulbs, the PCM thinks there is an issue.

 

Thanks, no LEDs and third is working, found a dorman replacement TPS and it seems to have fixed the issue