The ford dealership look and found a pcv tube or valve brokein

 

A clogged or cracked (broken) PCV on the 4.0 is almost always a PO174 code. If it has a PO171 code with it, then it is most likely at the MAF. If it is a single code then it is usually after the MAF. Just thought i should throw that out there for the next guy who might run into these codes. The PO300 code, random misfire, usually is a sign of a faulty coil pack. The V6 has a decent coil system, but they do sometimes go erratic, and set this code. If you can find another coil, (fits Mustang's Rangers, Explorers, Escape v6) and most other v6 Fords, so you would have no trouble finding a good one to test with.

One more thing. On these 4.0's, inside the throttle body, behind the butterfly, you will most likely find a ton of black crap from build up, and if you remove the throttle body, you will find the two holes clogged or nearly clogged. It's a simple thing to do, but you will find that cleaning it will make your car run like it came from the factory again. Google it and see what I'm talking about. This is where the oil separators come into play. Good luck.

 

Ok so the check engine light went off again and it says random misfire again I've changed my pcv valve so wat else can be causing the random misfire