I have A 1998 for ranger with 10k miles on a rebuilt motor new plugs, new wires, and a clean map sensor. the problem is that I get a check engine light within about 10 miles down the road indicating a misfre monitor fault.

"p1309 misfire monitor fault". Is this telling me that it acually misfired, or that the monitoring of a misfire is at fault and won't give me correct diagnosis.
sounds confusing huh? Well I can tell you that number four plug does misfire on start up because of an oily plug after a lengthy rest (over night). the threads will be heavly coated with oil and the spark plug grounding tab also wet with oil.
If I change the plug with a new dry one it still lopes for about 45 seconds.

I thought at first that the tappet cover was letting oil run down into the plug cavity and working it's way into the cylinder via the threads, but the hole leading to the plug threads is dry. Where could the oil be comming from to get the plug threads wet? The valve seal/guide leaking? not sure yet without a top end tear down

I can clear the mis fire code and continue down the road minutes later and still eventually get a misfire monitor fault code without feeling the engine misfire. I'm worried more about the oily plug threads than the misfire monitor fault, but would love to hear from others about both issues.

peace to all that have any ideas Tom

 

Hey Tom I have a 98 with a 2.5L and had a sorta similar problem read this maybe it will help. https://www.ford-trucks.com/forums/6...on-a-2-5l.html

 

That code is most often set by a bad camshaft position sensor signal.

 

I have found that the o2 sensor is bad and have changed it an now I'm fighting oil soaked plug from the valve seal and or valve guide, for now I'm just going to keep changing the spark plug. thanks for all your advice, merry christmas