Hi guys,
I have had this problem off and on for the past six months (or so), it is very intermittent and can go quite a while between occuring. The vehicle is a 1996 E350 with a 7.5 engine E4OD tranny.
Well it has been almost two months and 4000 miles and no problems till last week. Then all of a sudden the problem returned. Driving along fine about 50 mph and the truck just loses power and if you floor it is hesitates, sputters and wants to die. If you slowly apply pedal it will maintain speed and even creep up to 60. I limped home and a couple hours later had time to work on it. First I checked the fuel press, running 30+ PSI, removed vaccume and instant 40PSI, reattched vaccume and 30 again. Shut down and looked for loose lines, connections etc. 15 min later pressure still at 30PSI. Installed new TPS and hoped for best. Truck worked great for about 50 miles into work run and then started again, shut off for about 15 minutes then fine for another 45 minutes or so. Check engine light flashed once then never came on. Limped home and worked on it next day (don't get home till about 2 AM so too late to investigat at night). Drove around for about 30-40 minutes no problems but changed fuel pressure regulator anyway on spec. Truck worked great for about an hour the next nights work then started acting up again. The codes are for O2 sensor LH, but that could be caused by problem as it is definetly running okay then goes bad instantly. If sensor was bad it should not keep being good for a while then failing then good ten minutes later. The problem seems that it is engine comp temp related as it doesn't matter if it is +25C or -30C it is always about the same point into a trip (45-60 minutes operation) that it starts. So to date new(year ago), filters, plugs, wires, rotor, O2 sensor, fuel pressure reg, and TPS. I will soon have changed about everything. The only thing that I have noticed is a slightleak noise on start the goes away as engine wams up, will try and isolate this as may be letting false readings to sensor???
Oh well any other thoughts or maybe it just likes to work for one hour then take the rest of the day off (nice job if you can get it).
Seems strange that it will work so good for extended periods then start to act up.
Thanks for your input.

 

Have you tried changing your cat? They can clog up over the years, and will work ok for a bit then clog after driving a bit. This may not be it, but maybe something to think about. There was a similar psot here not to long ago and that seemed to clear it up.

CJ

 

No Cat it was removed along time before I got the truck. It worked fine without one for the first two years that I have had it as well.