1997 Ford Ranger running rough

I’m curious why I would have a cylinder 3 spark error if it were those two. Thanks!

p0303 is a cylinder 3 misfire code I think. Common causes for misfires are

  • spark problem
  • spark timing problem
  • fuel system problem
  • air induction or vacuum system problem
  • egr problem
  • pcv problem
  • compression problem

Since it is only happening on cylinder 3 apparently, most likely a cylinder 3 spark problem, cylinder 3 fuel injection problem, or cylinder 3 compression problem.

What was the result of your cylinder 3 spark testing?

I haven’t tested the cylinder 3 spark yet. Since you listed a vacuum and EGR problem, I wonder if that could be it since I get an EGR error also and their is not any vacuum on the hose that plugs onto the top of the EGR unit. I will trace down the vacuum hose and see if it may be stopped up or broken. Thanks!

The EGR valve isn’t activate at idle, so that hose generally won’t have a vacuum on it at idle. EGR problems will cause misfires though, but it would be unusual for that to cause only a cyl 3 misfire. More likely EGR problems would cause misfires on all the cyls. Some Fords have a gadget called a DPFE which is used to control the amount of EGR under various engine loads, and problems with that gadget (if you truck uses it) are sometimes reported here as causing these sorts of problems. Suggest you do the spark test on cyl 3 first though.