We have the same problem with our Nissan Almera Tino Diesel SDI, 52 reg. Had it to our Nissan Dealer 3 times, new fuel filter, replaced ball bearing in swirl valve and cleaned EGR valve and problem persists. Went to independent garage and they preplaced the MAS air flow sensor, problem still persists.
However I can reproduce the problem without fail, get the car nice and warm 15 mins does the trick and go down a steep hill doing 50 about mph, change down at the next roundabout and hey presto complete loss of acceleration. Stop for 5 mins and problem is gone completely and may not reoccur at all unless you go down another steep hill.
They fitted a ball bearing in the swirl valve, does this expand when the engine is warm, change position when going down hill and block something?????
Stop the engine it cools down and moves again, I dont' know is the tolerance on this ball bearing that small, any ideas?????
Lyn, Wells., September 2010