I HAVE AN 1986 FORD RANGER2.3 F/I ENGINE JUST REBUILT
BEFORE AND AFTER THE REBUILD. I WILL BE DRIVING DOWN THE ROAD AND THE ENGINE WILL LOOSE POWER AND START BLOWING BLACK EXCUST OUT THE TAIL PIPE AFTER A MIN. OR SO IT WILL STOP AND DRIVE JUST FINE. SEEMS TO DO THE SAME AFTER DRIVING AND SHUTING ENGINE OFF AND RESTARTING

 

Check for a bad O2 sensor. I had the same issue with my 88 Ranger with the 2.9 in it. Be driving along and then less power, look out the side mirror and see black smoke coming from the tail pipe. Always came and went as it pleased with no common occurance. Replaced the O2 sensor and all was fine since. It never set a code.

 

Thank you for the idea I will be replacing the O2 sensor asap will let all know results
thanks again

 

The O2 sensor does not cause an overfueling problem, it just tells you about it. I would think you either have a problem with the fuel pressure regulator or the injectors. This is not just a plug in part repair. It needs to be diagnoised by watching fuel pressure when the problem occurs to see if it increases at that time. If not, then maybe the injectors need to be cleaned.

 

An O2 sensor can cause an over fueling problem by telling the computer that it is seeing too much o2 in the exhaust. Too much o2 is a LEAN condition to the computer. The computer then compensates for this by increasing the length of the injector pulse to try and maintain a 14.7:1 air/fuel ratio. Thus a rich mixture and black smoke.

 

I am happy to announce that theO2 sensor was the problem. Not only has the black smoke totally gone away
but my fuel mielage has almost doubled I did have the fuel pressure checked out and it was good.But stoped short of pulling injectors. (money concerns) thanks for all of the input

 

Glad to hear your problem is resolved. Thumbs up to you for responding back as to what the outcome was. A lot of times one never knows if their suggestions actually helped to resolve an issue.