85 4wd wagon random cut out over 3000 rpm

[mtmtntop]

this random situation seems to be getting worse. i notice on highway over 50-55 mph. acts like a major ignition miss, engine just momentarily cuts out. have replaced fuel filter, coil, plugs and dist cap and rotor. i have not done igniter as i thought this either worked or did not (ie no start) could problem be fuel pump? otherwise car runs good. 205,000 miles, 33 mpg thanks

[Neu]

Does it happen if you're just in neutral and rev it to the same rpms it'd be at when you're driving at 55? like 2800 rpms i think.

[mtmtntop]

no it only seems to be on the highway. i don't think it has ever happened in any gear but 5th, and i downshifted to 4th as it got worse, still had the occassional miss. once it starts, it seems to happen more frequent. takes about 5-10 min of highway driving for it to happen for the first time.

[Neu]

So it's just cutting out? Just random mis fires pretty much?

[mtmtntop]

yeah. just cuts out, i lose power and have to slow down. i don't have to pump gas or anything like that to keep it going. but i find that i have to drive slower and slower to keep it from happening. that is why i am now suspecting fuel. yesterday, i had to go between 45-50 to prevent the problem.

[Neu]

definitely replace the fuel pump, it's a relatively quick job. Also run along the fuel lines to make sure it's alright.

definitely sounds fuel related, as you've replaced most of the ignition components.

[mtmtntop]

it does seem fuel related . i changed the fuel pump and noticed that it had been weeping so that was part of the problem. it runs much better now, but still has a slight miss under a load around and above 3000 rpm. i'm trying seafoam to see if that clears it up. autozone also suggested using brake cleaner to look for a vacuum leak. seems it may be related to secondaries in the carb. thanks for your suggestion.

[Petros]

This is exactly how a car acts with a partically blocked fuel filter. Since you replaced that check fuel pump, or possibley parically blocked fuel line, or carb supply. It is not too difficult to just remove the cover off the carb and inspect the bowl and float valve. Becareful not to loose the small clips and check valves.

It could still be electrical, but most of the obvious suspects you already changed out. I always keep a spare distributor on hand from a Pull-a-part type wrecking yard (only $7.50) and swapping out the whole distributor is a quick diagnositic tool faster than most others (and not too costly with a used distributor).

Good luck.