Having an interesting issue with my truck. Trying to load the engine under approx. 1K rpm, it starts to shudder, pedal goes dead, or at least no affect on the engine, real rough idle which drops to about 5-600rpm. Itll catch itself and jump up to a return idle. If I baby it and keep the rpms > 1K not to much an issue. Just for increased clutch wear.

Doing some research, I unlugged the fca, Had bad fuel knock. However it didn't do it Only tried it three times. Does this make sense? Still might not be the FCA. Any way to troubleshoot it? I hate just throwing parts at it.

Heres a vid:

http://vid12.photobucket.com/albums/a207/CrazyMoparGirl/IMG_4173_zpsv87d1i41.mp4

Got my ultra-gauge. When the rattle increases the rail pressure goes up to ~15k. Also showing p0251. Gonna get a FCA.

Ultra-gauge came in. Showed rail pressure jumping to -15k at idle. It also showed another code. P0251 iirc. Got a new FCA and so far seems to be fixed. Short test drive. Tomorrow I'll drive her to work.

How is it running now?

Glad to hear that the FCA did the trick, congrats!