I have a 1987 F150 XLT with an 8 cylinder engine. The truck has just over 200k miles, and has a brand new carburetor in it. I got it and drove it an hour home, on the freeway, and didn’t have any issues. It was running fine when I got it about a year ago, then decided to die on me while driving it about a month after I purchased it. After that, I took it to a shop where they did a full diagnostic on it and determined the only issue was the fuel lines. So we ran all new lines, and it ran great for approximately two months. We used it to haul a trailer in this time frame, and had no issues whatsoever.

However, now the truck has decided it doesn’t want to run while in drive. The truck starts (usually with only minor difficulties, as long as you pump the gas) and will idle fine. It sounds like the idle gets stuck sometimes, so it runs high but as soon as you give it some gas it runs normally. It can be shifted into reverse and neutral, still maintains the idle, but as soon as you shift into drive it starts to go a little higher, slowly gettin more intense until it just sputters and dies. It doesn’t matter if you shift it into drive and don’t move, just let it run, it still dies. We usually can get two solid minutes of running out of it before it dies.
Any ideas would be greatly appreciated, I’m at a loss as to where to start with this beast. TIA