ok, i just bought this 83 240 DL from a guy up the street who sold it because it was missing and he couldnt figure it out. basically, whats going on is when i first got it, it idled fine, but when i'd get it out on the road it wouldnt accelerate very well and you could hear and feel it missing. it was like it was randomly dropping a cylinder. so the dude put new plugs and a distributor cap on and that didnt fix it. it sat for a year maybe and i bought it. i took the old mass airflow sensor out of an 86 parts car i have and dropped it in the 83. now it wont idle well at all, and it stalls when downshifting. but after running it a bit, it got better, although it still stalls sometimes and still feels like its missing a cylinder when running. also it spits black smoke while idling, i cant see it when i'm driving it. and now it doesnt want to start, it cranks like once and goes cold. any suggestions would be very welcome, thanks.