mathaw

Hi everyone I am having this problem with my 1989 f150 5.0l 4x4 the problem just started this winter. From about 1000 to 2000 rpm truck cuts out and almost dies then backfires through intake. You can rev it up a little more though and it will get past that and rev and run fine until I let it idle again then try to rev it up again. I have replaced fuel filter and cleaned egr valve. Under a load its even worse I have to slip the clutch just to get the truck to start to move. But once it gets past 2000 rpm it runs just fine until I upshift again. And when I put it in 4 wheel drive truck does not want to move at all just spits sputters and back fires. Any suggestions anybody? I know that the timing may have jumped but if it jumped wouldnt it run crappy the whole time not just from 1000 to 2000 rpm?

Tacoma

you have a restriction in your exhaust

ymeski56

Cat back pressure is likely.

Especially common when running higher octane than 87, it is specifically engineered to run on.

dr_bowtie

check cap and rotor... you could have spark scatter... also check TPS voltage thru the sweep...

beings it is only in one part of the RPM range I'd rule out exhaust back pressure and anything valve/cam related... those would remain constant through the rpm range....

mathaw

Thanks for advice guys dont think its exhaust it has no cats and it has shorty headers im thinking it is pry something to do with distributor or icm

Mike Demny

I'm really thinking it's a cracked distributer cap....