Hey i have a nissan patrol turbo diesel 2002 automatic. It starts fine idles fine drives fine for a bit then wen at operating temp it randomly loses power and stutters and sometimes stalls. It also shoots smoke out of exsaust wen this happens. It also seems to mainly happen at higher speeds. Engine light came on also. It starts straight away again even idles fine straight after but once it starts happenin i need to leave it for a while or go like 70 or less to be able to drive it.if anyone could help ill be forever grateful its doin my head in
Only just bought the bloody thing n had to have day off i work away 
What color is the smoke when this happens, blue, black or white? Also, since the check engine light is on you need to get the error codes read. If you are in the USA this can be done for free at most auto parts stores. But I assume you’re not in the USA.
+1 to my 2 cents’ post.
But, as a general comment, when an engine starts & runs fine until it warms up, and it has no ignition system (being a diesel), I’d start with the engine temp sensor. If that smoke is black, it suggests that it’s running rich, and, being a diesel, perhaps the temp sensor isn’t telling the ECU it’s warmed up. Engines run rich when they’re cold and should run leaner when hot.
NOTE: this is just a wild guess.
Thanks mate i put it in to mechanic today im not hopeful on them fixing it ill post how it goes cheer. And the smoke is white that i can tell. Thanks