Surging and cutting off
Months ago I worked on an '04 f250 and replaced pretty much the entire high pressure oil system. Pump, the outlet fitting, stand pipes, those plugs in the heads, and one injector that had a bad o ring inside the fuel inlet of the injector. The truck has come back with a surge, both at and above idle. The surge is pretty extreme, it sounds like someone is really rapping on the throttle. It starts out pretty mild, and within less than a minute progresses to the point where it cuts the truck off. It will restart immediately, but if you keep running it, it gets to where it won't start easily.
I busted out my scan tool (bought when I was working on this truck before) and I noticed that when it would not start at all, the ICP was reading 0 during cranking. So, I disconnected the ICP on the front of the valve cover and it immediately started and ran fine. Plugging it back in, shutting it off and restarting, I got the surging. Unplugging the ICP while it is surging results in it immediately smoothing out and running fine, though it seems to be down on power with the ICP unplugged. I'm guessing that's because it's running on a table of assumed values that are pretty conservative? Oh, were no codes stored before I unplugged the ICP.
Anyway, I'm thinking it's a bad ICP, even though I replaced that months ago. What say you guys?