So I have a 1994 ranger with the 4.0 and a manual. It seems to be running rich and has a rough/ sporadic idle. When I started it today the down pipe was glowing red. I have replaced all 6 injectors and spark plugs, maf, tps, engine coolant temperature sensor(2 wire), crankshaft position sensor, air charge temp sensor and the ecm. It also has a hard time starting and doesn't want to stay running when warm. All the injectors are firing and getting fuel. I don't know what else to check or replace. Any help is very much appreciated, thank you.

 

Check the Vacuum hose on the FPR(fuel pressure regulator), if there is gasoline in there then replace FPR

Its behind the alternator down on the lower intake manifold, has the Fuel Return line hooked to it

The diaphragm leaks and vacuum hose sucks gasoline into the intake causing Rich running and flooded engine symptoms on warm restarts

 

I checked the vacuum hose on the fuel pressure regulator and it was dry. The cats were glowing red though after it ran for a couple min. Could it possibly be a clogged catalytic converter? And if so, what would happen if I just cut them out and straight piped it?

 

If MPG is down under 14MPG then Cats are glowing because of Rich mix

Its a Federal beef to run without Cats, $2,500 fine, but won't hurt the engine to do that, or effect performance one way or the other if Cats are not broken up inside blocking flow
Cats and mufflers can't effect performance if they are working as designed

Restricted exhaust shows up as limited power at higher RPMs as back pressure builds up, but won't effect idle or lower RPMs unless its a total block, i.e. potato up the tail pipe, lol
You can test for exhaust restriction using a Vacuum gauge on the intake manifold

CEL(check engine light) works, it comes on with the key and then goes off after engine starts?
And there are no "Rich" codes?


The fuel injectors all get 12volts with key on, the red wire at each injector
In 1994 the computer uses 2 Ground wires to open 3 injectors at the same time, its call Batch Fire injection
If one of those ground wires has a short to ground then you would get a flooded engine with key on

 

I tested all the injectors by putting a screwdriver on them and listening to the click and all 6 of them are firing. As far as engine codes go it throws a 117, 122, 112, 513, 565, and 556.

 

Did you look them up?

Or should I?

They are found here: https://therangerstation.com/tech_li...gitcodes.shtml

112 Intake Air Temperature (IAT) sensor is/was low or grounded
117 ECT sensor is/was low or grounded
122 TPS low (possibly grounded or open circuit)
These, all at the same time, would usually mean a problem with computer

513 Replace processor (PCM) (internal failure) <<<<, PCM is the Computer, so......................
PCM = powertrain control module, thats what Ford calls the engine computer, then and still

556 Fuel pump relay primary circuit fault - Power / Fuel Pump Circuits
565 Canister Purge 1 solenoid/circuit failure

If you have replaced the PCM and got the same codes then you got a bad PCM or you have a wiring problem in the main harness

On older PCMs its usually just the Blue capacitors that leaked, which can be repaired for under $5 if you can solder
Pop the top of your old PCM or the "new one"

Picture of your PCM here: Ford EEC-IV

And some of the wires you can test to see if they are shorted

Pictures here of replacing the capacitors: Capacitor Repair: Ford A9L ECM « Moates Support

You will need to sort out the PCM issue first this is not a hardware issue, i.e. injectors or Cats or O2s or fuel pump
These PCMs have a default mode which runs the engine Rich because its much safer than Lean which will melt the pistons, you are in "limp mode" as in "limp home" because something is wrong

 

i've been in your position. it wasnt fun. Ive done all the things that have been adviced to you. and finally i tore down the topend . I had a cracked head, and the other had a bad seat. had the work done and a brand new one. Still had issues. Came down to it. with no codes,it was a o2 sensor not reading correctly. $2000 later. it runs