Engine Problem

[Riding4eight]

Ive got a 1991 Ranger w/ 4liter. When you are at wide open throttle mainly on an incline you develop a misfire. Ive replaced plugs, wires, coil, fuel filter and that did not help. It idles fine and runs fine when you are light on the throttle. Any Ideas?

 

[Big Jim M]

Lots of ideas... Does it pop and crackle out the intake? Does it misfire as though it is running out of fuel?
Big JIm

 

[ForOffRoadDriving]

hows your fuel pressure and does it only do it on an incline or also when on flat ground?

 

[Riding4eight]

yeah it does have a backfire but it seems more like a spark issue other than a fuel issue. I havent checked fuel pressure yet but i will. It does it on flat ground if you get on the throttle pretty hard

 

[nooch450]

my ranger does somthing simular... havnt figured it out yet sorry

 

[Big Jim M]

yeah it does have a backfire but it seems more like a spark issue other than a fuel issue. I havent checked fuel pressure yet but i will. It does it on flat ground if you get on the throttle pretty hard

You havn't described a spark issue. A WOT backfire is usually a lean condition. Sometimes caused by a burnt intake valve. Perhaps low fuel pressure, or even a good sized vac leak after the Tb.
Big Jim

 

[sixty9oz]

did you figure this out? I have the exact same problem

 

[AllanD]

Before you get into complicated diagnostics... replace your fuel filter....

Yes, really...

AD

 

[sixty9oz]

already done