New member, Need help I bought a used 05 fx4 4x4 114,000 miles i have a issue with limp mode at idle, i am able to throttle up in park or neutral , but if its in reverse or drive little power i can get up to about 35-40 mph but it is not fun and i cant seem to get any codes out of computer. computer was reset before I bought it, It has new timing FOMOCO timing redone, with milling 340 hv oil pump, new ford vct solenoids, I hooked up to AUTEL 906 bt cant find and thing out of limits, no codes, no miss fires, replaced MAF sensor cleaned injectors, cleaned throttle body, new fuel filter, fuel pressure is about 38 psi, Oil is full , trans fluid full, the things i have found no power to fuse 23, 25, 35 , 36 and ignition switch has been messed with,

 

If the truck is going into limp mode, and your AUTEL 906 isn't showing any codes, I suggest taking it to a Ford dealer or the place you bought it from (assuming it was a registered dealer of sorts).

 

Go to a muffler shop and get your cats tested for blockage.

 

up date new data I limped around a neighborhood and got a few codes p0191 so i changed sensor, and p0171 ,p0174 and monitoring fuel trims LTFT are 29 +, i cant seem to to find vacuum leak with smoke test, injectors ohm out 12.4 to 14.

 

Fuel pump or FPDM. Check the FPDM for corrosion. It's on the frame rail above the spare tire, remove it and look at the backside, clean the connector. Change the fuel filter.

 

Fuel driver module intact. Very little surface oxidation, I looked at pre and post catalytic pressures 3 to 17 psi and main vacuum which was steady and fell off fast 18 down to 7. Catayletic converters plugged and when I looked down drivers side half had melted, although passenger side doesn't look as bad it still looks like it's my problem.

 

new cats, cleared pcm, no improvement in limp mode. ? flashing PCM