1993 f150 5.0 still running super rich. Looking at the engine coolant temp. sensor. It was supposedly changed, but i found 2 of the same sensors , same wiring plug on my motor and not sure they changed the right one. There is one by the coolant neck, left of the distributor, and one to the right of the distributor on the manifold. This on on the manifold is what they changed. my spare 94 5.0 from an f150 i have sitting in the shop doesnt even have this one. So my first question is which one is the engine coolant temp sensor?

Second question: How do you test it? my haynes manual says to test the resistance of the sensor both cold then hot, and make sure it is supplied ~ 5.0 volts from the PCM. So how does the PCM get the signal back? id like to test the signal its sending back to the PCM.
I think its showing the engine is dead cold and never warming, so thats why its loading on fuel.

 

The sensor for the computer has a two lead connector on it. One pin is power and the other is signal return to the PCM. The one for the dash gauge has a single wire connector on it.That one has no influence with the PCM's fuel calculations.

These are the ECT (the one for the PCM) specs from my Ford Shop Manual. I am sure these do not have to be exact but close.

58,750 ohms @ 50 degrees F
40,500 ohms @ 65 degrees F
3600 ohms @ 180 degrees F
1840 ohms @ 220 degrees F

 

Is the engine coolant temp sensor the one at the front in the coolant neck or the one on the dr8vers side of the intake. If not whats the other one

 

You have to look at the wire count for each sensor. Not sure but I believe the one at the coolant neck is the ECT.

 

I believe the one in the coolant neck is the CTS also. Rhey put the new sensor in the other spot, on the intake behind the distributor. It is also a 2 wire plug, exactly like the CTS. Would anyone know what this is?

 

Could be the air charge temperature (ACT) sensor. That sensor is not in the coolant passage.