I have a 91 ford explorer with a 4.0ltr that feels like it is missfiring. I have check compression in all cylinders and they are all with in 15psi, Replaced the computer and coilpack. Spark plug #5 was black and smelled like fuel, the rest of the plugs looked good. It's got plenty of vaccum. DO you guys Think its time to check fuel pressure??? and if so what would I look for?

Thanks
Austin

 

you might have a jammed open injector in number 5 cylinder