I’m an hour into a three hour drive and the car goes i to limp mode. Luckily I was going 30mph on a B-road at the time Restarting it fixed that and it hasn’t come back.
Pre-LCI E39s have both throttle-by-wire and a traditional throttle cable. Each has its own sensor. The ECU monitors both and goes into limp mode if a variance is detected between the two.
Google says it’s common for the cable to stick (mine does look a bit rusty) and causing this issue. I’m headed over to a nearby Walmart now to pick up literally any lubricating substance. Hopefully this is what fixes it and I don’t actually have a bad sensor. It’d suck if it cuts out again on the highway.