I have a 1992 318 Magnum engine swapped into a 1956 Dodge Regent. When it's cool, it will run pretty good, though it has a high idle. When it gets warm, the engine will start to misfire, drop cylinders, and make such little power that it will die when you put it in gear. I recorded what it does when it gets hot. In the second clip, I was losing speed while going downhill. I feel like it's heat related because it doesn't happen during winter, could it be the ECU getting too hot?

 

Coil or crank sensor would be my guess. Putting the pcm in the middle of the fire wall where it receives all the heat is not a good place for it.

 

I've already replaced the coil and crank sensor.

 

I'd put a timing light on the coil wire and verify it's loosing spark. That's what it sounds like.

 

I don't have a timing light, but I started pulling plug wires which showed that all of the cylinders had spark. I did find out that if I leave the hood open, it will idle just fine. But if I close the hood, it starts to misfire and idle high.

 

In the video the hood was open and it was still doing it. You will still get spark but it sounds like it's intermittent. A timing light will show that. From what i can see it looks like you have a lot of exposed wires, Might try wiggling the harness to see if that does anything. Do you still have the check engine light? If so you can do the key dance to see if you have any codes.

 

I meant that if the hood stays open when it's running fine it won't do it. I wiggled the harness and nothing changed. The only codes it had was TPS high voltage, EGR valve, and an AC problem. My neighbor is a Dodge mechanic and he figured out that the IAC valve was staying wide open which caused the high idle. He fixed it by unplugging the TPS, but it went back to the high idle after an hour.