Hey y'all. Im New here. I guess I'm posting in the right place. Have a 1994 ranger ext cab 4x4 auto with manual transfer case. Has 4.0 engine. Sitting there idling, black smoke comes from exhaust. Then all of a sudden it will cough and go to running right. Have replaced map sensor, tps sensor, crank sensor, auto idle control valve. Need some help please.
am a diesel mechanic by trade. So will probably understand what you tell me.

 

Avoid parts swapping if you can. You can introduce new problems with cheap aftermarket parts. But i know, its easier to stab at a problem that way verses the painful process of troubleshooting. Gettign that TPS sensor set back up can be tricky but im sure you got it dialed in correctly since your a diesel guy.

Black smoke is rich condition. Here is some ideas that come to mind:

Look into fuel pressure regulator and vacuum hose for it. Put a gauge on it fuel rail and measure and see what actual PSI is. There is a test you can perform on reguluator, i think you pull vacuum line and measure presure. Make sure vacuum hose is good.
Read those plugs for each cyl. If one plug is darker than other, that cyl is running rich. Could be that corresponding fuel injector is bad or clogged where its dumping uncontrolled fuel.

Thats where i would start! Im not too smart so maybe others can chime in with better ideas.

 

Sorry, you probably wanna check those plugs first to see if its a system wide issue or just related to a cyl before going any further.