1987 2.3 FI giving fits. RUNS RICH intermittently

1987 Ranger 2.3 FI , mfg 8/86,140K, that is running rich ( BLACK SMOKE)It starts after it reaches warm up- usually 7 or 8 miles driving, sometimes farther the colder the engine and weather is but on recent warm day - 65 degrees-it drove FINE. After that it sucks the gas and starts smoking black,sputtering and jerking. I have to drop it down a gear or two to continue.Mileage has dropped dramatically. AFter driving 40-50 miles ,parking for a few hours it doesn't seem to do it! When I rev it in neutral or with with clutch depressed it clears up momentarily but when you try to maintain speed it reverts right back . ALSO- it will idle rough but then of its own accord it will instantaneously run fine and sometimes do the same while at highway speeds! This condition has progressed somewhat over time.

To date :

Tryed to check O2 sensor BUT IT DOESN'T HAVE ONE. I looked 3 times and mechanic checked it from underneath and said it did NOT have one! NO WIRE running to manifold either so it's not hidden.Not a CA vehicle. WTH?!??

Replaced ECU but did the exact same thing so I reinstalled original( took new ECU back for a refund- WOW !)


Swapped MAP sensor from my 1994 351 Ford E350 and saw an improvement - about a 6 or 7 on a 10 scale but problem still exists

Replaced TFI ( had new one laying around)

Checked timing- OK no help though

Bypassed EGR control - still had same problem

Cap , rotor, wires & plugs replaced - it was due for them anyway- no effect
Installed new coolant temp sensor, the one the ECU monitors . No help there and $13 poorer

Checked vacuum hoses, PCV and replaced suspicious ones- no help

Squirted oil around intake gasket to check for leak- nada!

Checked for codes but got only 52 (power steering press switch) and 67 ( !!!)

Did wiggle test on all sensors and unplugged one at a time - Nothing!

Checked ground- OK

Had a REAL mechanic look at it and he is stumped as are 2 other mechanics in his shop. I bought truck NEW in 1986
and I'm driving it another 22 years so if you can help...PLEASE???

engines usually smoke for an internal reason that old computer wont help.Rings might be an idea but black smoke. is it getting hot(overheating)? sending unit might be bad or oil pump itself

oil pressure fine , cylinder pressure fine. Black smoke is FUEL ...oil smoke is blue. Most internal problems would manifest themselves continuously .