My '87 ranger with a 2.9L with 170,000 has a problem I'm trying to troubleshoot. When driving down the road it will suddenly start missing and puking black smoke out the exhaust like it's burning too rich. then suddenly take off like nothing is wrong. I just changed plugs, wires, cap and rotor thinking maybe an electrical problem but it does the same thing.

maybe something with the cold start choke? unsure of where to troubleshoot next. all wiring looks ok.

any help would be appreciated. thanks in advance.