dyurisich

Guys, been having an issue for the past 3 weeks. Whenever I run the truck, 2008 XLT 5.4, through the wash with underbody spray and leave, I'm experiencing what feels like hesitation or surging of power. The RPMs don't change, but feels just weird. No codes thrown.
Will return to normal if the truck sits for 15-30 minutes.
I'm thinking something electrical like transmission speed sensor retaining water...any ideas?

joe mcmillan

Check your FPDM for cracks or corrosion. It's located above the spare tire. Drop the spare and then remove the 2 bolts holding the FPDM so you can inspect. New ones about $59 on Amazon or more at your local auto parts.

dyurisich

Ok thanks. I replaced the original about 4 years ago with a Dorman model but will check this one too. Need to check the air in the spare anyway.

650NutKase

FPDM is my guess as well. The electricals are all pretty well sealed from the elements, and the pressure from underbody washes aren't typically that high.

techrep

iTrader: (1)

X3 fpdm

dyurisich

FPDM looks ok to me...

650NutKase

check under the engine and start gently tugging on wires to see if one is loose. They are all sealed with rubber gaskets, so there is a possibility one isn't plugged in all the way and allowing moisture in. Also, is the air intake tube connected correctly? Possibly getting water in the tb?

dyurisich

Thank you I will check wires under engine. Just cleaned MAF yesterday so I know air intake is good.

dyurisich

Well can't find anything loose. Have to keep researching...thanks again

650NutKase

vacuum leak somewhere? Adding moisture to a vac leak can cause the engine to stumble.