I am having issues finding my problem with my 2000 F150. It only acts up when I have it in gear and getting up in between 45-60 mph. I have replaced most of the spark plugs and coils packs am moving on to replace just the rest of the plugs to go the cheap route first. It has a code but is only coming up with a generic misfire code of P0300. I've checked for vacuum leaks and cant find any. If you have any ideas please let me know

 

Misfire under a load is more often than not a plug problem. What brand of plug are you running? These engines like Motorcraft. It's also important to get them all changed out.

 

After finishing replacing the coils and plugs, the problem will most likely be solved.

 

I am running auto lite plugs and I have heard of the issues being caused by a catalytic converter but I'm unsure on that one either.