A common problem on the 2.5TD Cherokee is the number 1 injector. It has a wire coming from it which sends a signal from the position sensor in the injector to the ECU. When it stops sending a signal, the engine goes into a crude limp-mode and limits revs to 2k rpm.
A very long time ago, I learnt this because it went into limp mode. I detached the wire from everything else and played with it, reconnected it and for 15k miles, it has been fine. However, today it is now back in limp-mode.
I wonder if the really cold weather this morning has anything to do with it.
I guess it could have got some moisture on the delecate connection..
So, I have the special injector socket on order and I need to find a reasonable Jeep breakers for one of these: