I recently bought a 2000 Pathfinder diesel pickup (2.5L) I drove it home and it was going ok for the first 2.5  hours, but for the last hour it started losing power and would not rev. I had to stop and when I tried to start again after a minute or so, the revs came up, and also a cloud of blue smoke from the exhaust. The same pattern repeated itself for the rest of the journey and I was relieved to get it home.

      What could be causing this problem?

I would first check the fuel filter - replace if in doubt

Otherwise sounds like the turbo variable vanes are gummed up with carbon but this usually puts the engine into limphome mode accompanied by an amber engine warning lamp on the dash

Sorry for late reply.

Can you tell me where the vanes are located?

The vanes are located inside the turbo and can be cleaned using a cleaning solution in situ

https://www.ebay.co.uk/itm/292459335127?_skw=turbo+cleaner&itmmeta=01JC60BMWEXRSD20EMHAM2ZFK6&hash=item4417ef4dd7:g:wcwAAOSwvShajqeM&itmprp=enc%3AAQAJAAAA0HoV3kP08IDx%2BKZ9MfhVJKlEsMwj%2F9Rwy31LfWXY0vu7JPmLf9xI%2B%2BMMJNw2%2BBAV%2FAzGfwovr4g0y%2B3nTHJ4Prps1SHhzuT%2Ff2g2nWknOStqIPX6QYXX8mYiOwrPQZg0rCbLgkZPxW2e%2Bb%2FYuW1DwD1hTh1Pxnmpzlv3q%2Bmbox0A19ibnfkcrcj6SmcyxcJgPmsnqSNrib3vGE5upPP8XDzI8lnokXOTc44%2FUuHtUlQmJoH0yyaUgDzXcWukxhKo4OnzBu0ua0dem9Pz9hohvhw%3D|tkp%3ABlBMUKrOrsDhZA