Im working on a late 99 7.3l at work. It came in as a no start, or start then die in a few min and wont start back up. It has two ICP codes. 1211 and 1212. the owner tried a new ICP sensor, same problem. The oil is clean and full. It got towed in and it started right up. Ran perfect, very responsive and could spin the tires brake boosting it. I let it run for about 25 min. I shut it off and tried restarting agian. started up, but had a extended crank and ran very poorly. No power, very sluggish and would think about spinning the tires brake boosting it. I shut it off again, no start. I took the IPR valve out and cleaned it. Started up and ran good again. Shut it off, no start again? WTF? I think there is something wrong with the IPR valve.