I don’t know where else to look and could use any of your fine expertise or suggestions.

I bought the 1988 Ford Ranger in a pinch because I needed a truck for a month. I knew it needed work. I bought it knowing that it would “buckle” and “jerk” while accelerating and that it ran rich (black smoke out the tailpipe/gas aroma). It’s running so rich that my catalytic converter is rattling inside the housing). It’s fuel injected so I can’t adjust fuel to air ratio. I’ve taken it to 3 local mechanics and 1 Ford dealership. All of them said they were stumped.

here’s what’s been done with result, “issue persists”:
Changed plugs and wires.
new rotor.
replaced MAP sensor.
New EGR.
repaired all vacuum leaks and passes vacuum test.
Replaced IAC.
Ensured all fuses ok.
checked fuel shut off and it was not tripped (the one under dash).
coolant temp sensor measures within spec.
fuel pressure at 43 psi.
Replaced fuel pressure regulator.
Replaced low pressure fuel pump in tank.
Replaced high pressure fuel pump in frame rail.
Replaced fuel filter.
Replaced all 4 fuel injectors.
Replaced O2 sensor.
Ensured engines timing is correct.
double checked with Ford that fuel injectors were correct.
physically cut out CAT and straight piped to muffler.
deleted muffler and cat to check for exhaust back pressure.
I ran Seafoam through the vacuum lines while running (white smoke galore)
Replaced trucks computer.

In all the above scenarios the truck is running rich. Black smoke out the tailpipe and an overwhelming gasoline smell.

what in the HECK am I missing?

any ideas on where to go next? Thanks I’m advance

 

Welcome to the forum

Going to be hard to diagnose because of all the "new" stuff
New means NEVER EVER TESTED now-a-days, lol
30 years ago it meant "tested and works"
Now its a crap shoot on whether or not a "new" part can be trusted

1988 2.3l is fuel injected but last year with a distributor and 4 spark plugs

So Rich running would show with smoke out the tail pipe and darker brown spark plug tips
Blacken spark plug tips can be oil leaking in, from valve guides or rings, and would cause smoke out the tail pipe as well
But easy to tell the difference by looking at spark plug tips

43psi fuel pressure is high for running engine, but correct with engine off
Running pressure should be about 30-35psi, engine vacuum pulls open FPR(fuel pressure regulator) a bit to lower the pressure
This vacuum line on the FPR can also be a source for fuel leaking into the engine and causing Rich running so check it for fuel
"new" FPR means it can leak, lol, but very easy to check its vacuum hose

Leaking injectors
Turn key on
Press gas pedal down to the floor and hold it down
Turn key to START
Engine should just crank and NOT start, not even fire, injectors are turned off

Its called Clear Flooded Engine mode/routine, all fuel injection computers have this
0 RPMs and Wide Open Throttle(WOT) = shut off injectors to computer

Spark is still on so if there is fuel leaking in engine would fire

This test assumes computer is getting WOT signal from Throttle Sensor(TPS)
So if engine starts then key off, use a stick to press down gas pedal all the way and go to the engine
See if you can open the throttle manually a bit more, if so throttle cable is stretched, easy fix, Google: Ranger throttle cab Mod

Report back after test

1988 2.3l will be Batch Fire injection, this means computer opens(grounds) 2 injectors at the same time and just alternates each set every 1 RPM
So there are only 2 control wires for the 4 injectors
All 4 injectors get 12volts with key on
Computer then starts to ground the injectors using the 2 control wires when there is a Timing Signal from the TFI module(spark module)

If you think injectors are leaking unplug computers 60-wire connector
Try to start engine
It should not start of course, but if it fires then one of the 2 control wires may have a partial short to ground causing those 2 injectors to leak
If it is a no start then wires are good but could mean an issue with computer, new or not

 

thank you for taking the time to reply.

all spark plugs show black carbon buildup - looks just like what’s coming out of the tailpipe. Rich condition. See pic.




i did the WOT injector test - at first no ignition. Just crank for about 5-7 seconds. Then it started cranking with fuel to air mixture. Then I was totally on. I got a stick and had the pedal at WOT. There was play at the throttle under the hood. I got about two zip ties on the pedal. Double checked under the hood - all play was gone.

tried again. On. Pedal all the way down. It started right up. I swapped computers. Did the injector test again, and same result. Starts right up without even cranking over. These injectors have less than 30 miles on them and the spark plugs ALL show signs of rich condition (it’s not just one or two of them). What are the odds of all new injectors leaking? Could it be something else causing the rich condition?

 

I unplugged the wiring harness that goes to the computer - completely disconnected. I cranked it over and it started for a second and then died. I kept trying to start it and only got cranking. No ignition. Does this indicate a short in the wire? Or was it just clearing existing fuel in injectors?

 

With no computer hooked up there is also no fuel pump so no fuel at injectors

Check the Fuel Pressure Regulator(FPR) vacuum hose to make sure there is no gasoline inside it

To repeat the no computer test you need to "hot wire" the fuel pump, but its way easy to do that

Locate the OBD1 test connector in engine bay on main wiring harness
Then look here: https://www.therangerstation.com/tec...ry/OBD_I.shtml

In second drawing Fuel Pump slot is labelled
That slot is the GROUND for the fuel pump relay, normally the computer grounds it with key on for 2 seconds, to Prime the system, then grounds it full time when RPMs are above 400, cranking speed is 200rpms
So if you use a jumper wire from battery negative or another Ground to that slot, then when you turn the key on, fuel pump relay will close and fuel pump will be on and you can repeat your computer unplugged test

If FPR vacuum hose is clean, no gasoline, and engine fires with computer unplugged(fuel pump on) then you are down to a leaking injector(or one of the 2 injector ground wires is shorted to ground)

New means NEVER EVER TESTED, not tested and works, that was lost about 25 years ago and replaced with warranties when labor prices got too high for good quality control

 

Not quite sure what to make of this:

engine cold.
Disconnected computer.
jumped/grounded the fuel pump at location on pic.
I go inside vehicle and engage ON position.
I can hear the fuel pump running so I know I jumped it. I crank and it will not start.

I plug back in computer. Do the WOT test and truck starts with gas pedal all the way down. I wait for it to get to temperature and turn off vehicle.
i immediate disconnect vacuum hose to FPR. Dry as a bone. I even put the hose to my lips and suck (not recommended) to see if any gasoline vapors are present - none.
Disconnect computer.
jump wire to fuel pump ground.
redo test at temp. Issue persists - unable to start engine. Just cranks and cranks.

not sure what that means. Any ideas?


UPDATE:
I started thinking… with the no-computer test (we’ll call it), it proved that both the injectors and the wires (grounded/shorted) were ok. So I started thinking about why it wasn’t detecting WOT with the computer connected and my brain thought of the TPS (Throttle Position Sensor). I took apart the throttle body and it was extremely dirty. Black suit. A bit of wet amber oil. I took off the throttle body and cleaned it. The local auto parts store did not have a TPS sensor for this year so I’ll order one later. Anyway— I put it back together and it feels a bit more responsive but still black plume and gasoline fumes when pressing the gas pedal. Idling very rough - just chugging along. So issue is still occurring.

 

If engine didn't start with Fuel Pump jumper in place, and no computer then injectors are not leaking nor is FPR

So no shorted ground wires

Do the injectors look Stock, i.e. OLD, lol
If someone put in larger injectors then..........Rich running
Computers(PCMs) are programmed for engine size, fuel pressure and injector size(like 14lbs/hour)

Gasoline's 14.7:1 air:fuel ratio is a WEIGHT ratio
14.7 pounds of air to 1 pound of gasoline
14.7grams of air to 1 gram of gasoline

So fuel injectors are rated in how many pounds(lbs) of gasoline they can flow in 1 hour
Larger injectors without reprogramming the computer, just means a Rich running engine not more power

I am stumped on why you are running Rich

 

injectors look brand new.
I even cross referenced the part number used with Ford and they agreed those were the corrected spec injector.

if I cleaned the throttle body and the spark plugs, O2 sensor, etc. are coated in carbon/black suit, would that cause the rich condition?

 

Did you ever figure out the rich running issue? I’m having a similar problem. Nothing seems to affect the rich mixture short of shutting off the fuel pump