great site, been searching and can't find my exact prob or fix here. I have an 05 f350 v10 2wd w/ 96k miles.had a new ford tranny installed at 50k, i have a canteen truck body mounted and just last month or so when i get to a grade or any real load situation I lose all power, truck won't rev over 2k rpm and starts pinging and misfiring. also speedometer works on and off.i had it on a scanner at a shop, it showed i needed 2 coils, so replaced to 2 coil, plug and boots, no more misfires b ut still no power under load.I replaced fuel and air filter, no power, went to diff shop and mech came up with p-0661 code, did test twice same result, so intake manifold runner control now ? i am selling this truck soon and do not went to throw money at it needlessly, i am not convinced this is the prob, i think it may have a intake leak as i sometimes smell antifreeze burning, oil looks fine tho and af is full. Any ideas ? i read some other threads and wonder what relation of speedo not working is ? cat checks out and erg specs on scanner were fine, also there is no regular erg on this v10. Sorry for the long winded post put i am a worrier

 

giving you a bump.

 

Well one way that I have used to find intake leaks in the past.
It's not the safest way. But get a SMALL propane torch with
a hose. DO THIS OUTSIDE. start truck and get it warmed up.
make sure all the plug boots are good and in place. Turn on
the gas but don't light it. Point the nozzle around al the intake
and listen for changes in the why the engine is running. When you
hit a spot that is leaking you should get a change in the way it is running.
It may help if you have a good tachometer and someone watching it for you.

Hope this OLD trick works.

Sean

 

just bumping this up and hoping for some answers....

 

Speedometer problem could be due to an acting VSS (vehicle speed sensor ) which is located on rear differential cover . Some claimed success by just cleaning it , some changed it when mulfunctioning.

PCM takes the speed data from VSS and shifts the tranny accordingly . So, it is possible that your lack of power could be due to acting VSS sensor . Check it out .

Good luck,

 

wel started truck friday morning , got about a mile and lost all power, ran terrible and cel started flashing, so I limp to my mechanic, a 3rd one now, who
diagnoses I am running on 7 cylinders, 3 coils went bad overnight, so mech replaces the coils and suggests unbolting the cat and driving it to see, well that was it, had all power back, loud as hell though, went to a exhaust shop and had a cat welded in, took out the old cat and tried to shine a flashlight thru it and couldnt see any light at all! So all along 2 mechanics told me it wasnt the cat because it never glowed red, didnt bog at low rpm and didnt throw a cel. So 3 plugs , 6 coils, a fuel filter and a cat later it seems to be fixed. I know bad coils kill a cat, but can driving with a really bad cat kill the coils ? anyways, sounds like a Viper now with the burbling V10. Hope this helps someone.