I have a 1992 e150 with a 5.8 l engine. 140,000 miles.just bought it at an auction. while driving it home it has a misfire cousing bucking. at an idel it surges and misfires. I thought a tune up would solve the problem.
I replaced plugs, wires, cap and roter, fuel filter. but no fix. so i cleaned egr and replaced a few bad vacume lines. no fix
a little fustrated i took it to a ford dealer. after 2.5 hrs diag time, i was told it needed a new pick up sencer and a icu. so a yanked the distributer and instaled a new pick up coil and also replaced the ig. control unit. but guess what? dident fix it.
so now i am guessing and replaced the tps dident fix it either.
nex i ran a can of seafoam through it and dumped some down the main vac line and let it sit for a while, but that dident fix it either.
this morning i took it to another shop and this mech. put it on the scope. when it missed, the scope showed that it was goin dead on all cylinders.
so i replaced the pcm relay, but that wasent it. so im gonna try the pcm itself. unless im wrong and just going to dump another 150 bucks for nada
does it act this way all the time or only after it gets warmed up? whats the timing set at? have you attempted to pull codes yourself using the paperclip method? Ford Fuel Injection is a great site showing you how and has loads of usefull info.
You really should check the codes before throwing random parts at a problem, because as you said, you're really just guessing.
However, from the symptoms, I would guess it's s fuel pump. This is an e-series van, right? I don't know as much about the vans, but I know in 1990 they got the in-tank high pressure pump as opposed to the earlier external pump. I would guess your van is the same way. But you really need to check the fuel pressure as well as the codes.
I guess this was the long way to say, "do what he said".
it starts misfiring as soon as the engine rpms drop after cold start warm up. checked for codes last night, but dident get any due to pulling out pcm to match one up at the parts store. im installing new one today, ill post the results
sorry to dig up an old thread but what was it? i have a 93 same thing, i had a spare motor and did full tune up, swapped dizzy and module, plugs wires cap rotor fuel filter tps oxygen sensor nothing, only things left are fuel pump (30 psi, 40 with vacuum line off) 18" of vac at idle, it bucks surges and stalls. thanks
Mine did the same thing but only at cruise and under a load, i did lots of work to the exhaust and that helped a lot but it still does it just not as often, i am leaning towards fuel pump or MAP sensor or both..
MAP sensor is the brains of S/D EFI which the 1992 E150 with 351W utilizes..
The fuel pump could also cause a problem like this, it can intermittently fail and cause drops in fuel pressure which would certainly cause bucking on a fuel injected vehicle..