Toyota Surf 2L-TE problem

My toyota surf 2.4 TD 2L-TE engine making noise and blowing thick black smoke. It idles fine at aroud 700rpm but when you give a little blip of the throttle it seems to stick for a few seconds at around 1200-1500rpm and runs rough and blows out thick black smoke before dropping back to normal idle. Also engine check light comes on and after diagnostic it give fault code 12 which is (timer control valve). Not sure of what is causing it tho, possibly fuel pump? fuel filter?