help

[mourne14]

have an 03 xtrail 2.2 180,000 miles, haven't driven it much since I got it about 2 months ago, about 300 miles, drive a van for work and don't drive much when not working. have friends over at the minute and took them out into the mournes all road work but up hill and down dale things went fine for a while but after about an hours drive anytime I accelerated hard  to get up hills I got thick black smoke out the back when I eased off the accelerator and on level ground things were fine it was only when I pushed her hard I got black smoke and a clatter/rattle off the engine. any advise?