Ford Super Duty (1999-2016) :: Random High Idle Sometimes When Put Into Park - Codes P0300 And P0401

1999 F-250 V10 .... Truck was running perfectly fine except for a random high idle sometimes when put into park but if I gave it a good rev it would drop back down to normal. I assumed it was a dirty IAC or something and figured I'd get around to it later kinda deal. I also had a coolant leak from what I thought was the intake manifold to head gasket on the drivers side right in the front where the upper radiator hose meets the intake manifold so i added water here and there no issues.

One night I need to pull a trailer and didn't have the wiring set up for it in the back so I stopped at advance auto and bought one of those kits that plugs into your brake wiring harness and then plugs into the trailer. I tested it in the parking lot with the trailer and it was all sorts of messed up. My reverse lights stayed on my brake lights didn't work either etc. Turns out it was for the wrong years but plugs matched up coincidentally. I returned the kit and drove home just fine.

Next morning on my way to work truck started misfiring like crazy idle was bouncing all over the place lack of power etc. I took it to advance again after work even though no check engine light came on I still pulled 2 codes. P0300 which is multiple random misfire (no specific bank) and a P0401 which is an EGR Insufficient Flow code. I took it by a local shop I get my oil down at and they told me it was probably the fuel pump that they go bad in these trucks alot.

So I replaced the fuel pump and the fuel filter. Nothing changed so I thought maybe that coolant leak had dripped down to the plugs or possibly the intake gasket was getting worse and leaking coolant into the air flow ports since it was thought to already be a problem. So i pulled everything off the top and firgured id go through it all why I had it apart. I replaced the intake gasket but noticed when i took it apart that it wasnt the gasket that the head it self had a small pin hole leak in the very front where the coolant fed into below that upper neck that bolts to the intake manifold. I patched it with jb weld/ quick steel/ and rtv. Yes I know it wont last but just for the time being until I figure out the main issue. Replaced the plugs with motocraft plugs checked all my coils for grime and corrosion or what not and they all seemed fine and cleaner than expected. replaced the gaskets and threw it all back together. I also cleaned out the EGR and IAC with air and brake cleaner etc.

Blew all my lines out with air and everything seemed fine. I also replaced my DPFE sensor. Started it up ran fine at idle for like 5 min no coolant leaks or anything so I thought I was golden then about 500 ft through the neighborhood on a test drive the exact same misfire came back doing the same thing with the idle etc. I'm going to check my fuses tonight but I'm starting to think that maybe when I plugged in that wrong wire adapter for the trailer that I may have screwed up something with the PCM. Only because the lights were all out of wack and literally the next morning I started having these issues. I'm lost if its not a fuse. I would really hate to buy a PCM and not need it especially after all the parts I've bought and not needed already.

The vacuum lines all seemed fine and intact as well with no cracks or leaks.