94 ranger 4.0 wiring help

[red081382]

I recently done a head job on my ranger and now it's burning through gas like water like five mpg. My check engine light keeps giving me o2 and canister purge cylinoid codes even after spending almost two hundred bucks replacing them but while replacing o2 sensors I discovered that there is a black plug an tail end of wire harnest just hanging there and I have no clue what it supposed to go to please help it's located where the transmission harnest and the two o2 sensors hook up I have looked for a diagram with no luck maybe someone could help me figure out what it goes to and what my problem is I am thinking it could all be tied back to that missing connection

 

[RonD]

5mpg, that's pretty good for a 4.0l Ranger, .....................just kidding.

O2 sensors can't cause that type of fuel issue, these are for fine tuning fuel mix.

I have a few unused wires on my '94, one I know is for an automatic trans, I have a manual, unused connector is just above the bell housing.

Fuel system and lean/rich is set by the MAF sensor on the air filter housing, make sure it is connected, 4 wire connector.

Also playing a major roll in fuel mix is the ECT(engine coolant temp) sensor, this is a 2 wire SENSOR, not to be confused with the 1 wire SENDER used for the dash board temp gauge.
The ECT sensor is used by the computer to tell if the engine is cold and needs to be run rich with a high idle, Choke Mode.
Make sure this 2 wire sensor is hooked up or you will get a CEL and run rich all the time, so driving around with Choke on.
This sensor and the sender should be located near each other on the front of the lower intake, by t-stat housing.

Check the Fuel pressure regulator(FPR) on the fuel rail, it has a Vacuum Hose attached to it, remove this hose and check it for fuel or fuel smell, replace if fuel is in there.
If FPR diaphragm is leaking fuel will be sucked into intake and MPG will go way down.


What are the code numbers?
Codes rarely mean you need to replace expensive parts or sensors, codes mean sensors are working and a problem has been detected.
EVAP system codes are usually from cracked vacuum hoses, they are just old and brittle so crack and leak.
Filler/vent hoses on the gas tank also crack and leak, so EVAP codes will come up.