Truck is a 95 4.9 5spd, 148K miles. Recent tune-up with motorcraft parts. I drove a bunch Saturday, nearly 200 miles before the problem showed up. I had just filled both fuel tanks and headed for home. I had gone about 50 miles down the freeway cruising at 70+ about 2300rpm when I came into a driving rain storm. The engine cut out for an instant and soon after that the check engine lite came on. The lite came and went a few times, then the engine started running like cr@p. It was bucking and losing power and speed. I pulled to the right lane and it would hardly make 60 MPH. I downshifted to 4th to see if higher rpm would make a difference (it didnt). Thought I was goiing to be stranded on the side of the freway in the rain, but on a whim I punched the fuel selector to the rear tank and instantly the problem went away. Truck suddenly drove fine again. After 5 miles or so I switched back to the front tank and it still drove fine but the CE lite was coming and going again. I made a stop at a store for 15 or 20 minutes and when I headed for home again the CE lite didn't come on again.

I pulled the codes and got 171, 172 & 181 from the CM. KOEO 522 KOER 111

A couple of possibly related issues. Two times on early morning cold drive-aways the truck has started the bucking and losing power stuff( no CE lite). I could pull over and turn it off and restart and it would then run fine. Also when switching tanks there is sometimes an instant where the engine cuts out. Is that normal?

I know its a long post but I tried to cover everything. Any ideas? Thanks!

 

It sounds like a dying fuel pump to me. The lack of proper fuel/air mixture could have tripped the check engine light.

I would get a fuel pressure gauge and test the fuel pressure at the rail. If it's abnormal, replace the fuel pump. They're in the tank, so it's a bit of a job, but nothing you can't do in an afternoon.

Then reset the computer (disconnect the battery) and if the problem crops up again, pull the codes and go from there.

 

May have a bad check on the front tank. The reason in runs fine on ft but not rear. On the rear tank fuel may be leaking by into the front tank, keeping the pressure low.