I just bought this truck 1998 f150 4.2 v6 ext cab automatic 2wd.

I replaced the ect(engine coolant temperature ) sensor and found a plug unplugged on the same harness just before the ect plug(going towards the front of the engine) . And a broken sensor plug that fit in the harness plug? But I don't see where it goes .

I replaced the ect sensor cus the dash wouldn't read any temperature .

And the truck has a stumble at idle and a slip when shifting from 3rd to overdrive then after a few seconds of the engine reving up like it's in neutral it goes to overdrive and all is well till it shifts again to overdrive

 

I have 2000 with the same engine/driveline. If you can post a picture I'll look under my hood for you. If you want to send it to me direct you can at marc.dellario@gmail.com
Your OD shifting issue may be elect. solenoid on the tranny and nothing to do with this missing sensor.

 

Here are some pics of the broken sensor I found it fits right in the plug. . In the last 3 pics u can see the engine coolant temperature sensor and just befor it on the same harness is the plug I can't find out

 

Is this it ?
The broken off end 2 wires may be hanging down below. Or from crankshaft sensor ?

 

I'll check later today after work. mine don't look like it's long enough to go to the left passenger side of the water elbow like that. Can U tell if the plug groves are the same.
1 tab on left and right towards the top and one on top offset to the left.

 

Looking at the way the fastener is broken off, It probably plugs into the O2 but you should have a code if so. It may be that the O2 was replaced and rewired with the plug just cut off and left there. The way Universal O2 hook up are different from factory if so.

 

Almost seems like it might lead under the intake manifold . That photo u posted PAPA TIGER is the right harness but farther past the zip tie u pointed out. it might look like the knock sensor harness maybe .but like I said I think it's forther up past the zip tie

 

The open female plug would accept, intake runner control sensor. Top picture is another type.





Can this help ? You will probably have to partially disassemble to find out. Gaskets and capscrews are probably needed anyway. Obviously there is a gray area for 1999/2000 and may have either possibly electric or vacuum ? Possibly a 2000/2003 motor installed in the truck possibly with its wire harness ? Your truck should have a vacuum system and probably does with the parts there underneath it all. The wire harness would be wrong for your year then but in the truck anyway. With your running problems there are probably issues in this area maybe disconnected rods or hose.
I would pull the top half off to find out what is there to satisfy myself.

 

It looks like the last plug u posted but the groves on the side are even not offset .
I hope to pull the intake off tomorrow and take a look . Any one hot a diagram to take the intake off

 

Disconnect the battery


Upper Intake Manifold
Removal
Remove the engine air cleaner outlet tube (9B659).
Disconnect the following ignition coil electrical connections.
Ignition coil electrical connector (A).
Radio ignition interference capacitor electrical connector (B).
Remove the bolts and remove the ground strap.
Caution: Spark plugs wires must be connected to the proper ignition coil terminal. Mark locations before removing spark plug wires.
Note: Refer to the cylinder to coil tower relation indicated.
Disconnect and remove the six spark plug wires.
Disconnect idle air control (IAC) valve electrical connector.
Remove the accelerator control splash shield.
Remove the two accelerator control splash shield bolts.
Remove the accelerator control splash shield.
Disconnect the (A) accelerator cable end and, if equipped, the (B) speed control actuator cable end.
Remove the (A) accelerator cable to bracket bolt and, if equipped, the (B) speed control actuator cable to bracket bolt and position the (C) accelerator cable (9A758) and, if equipped, the (D) speed control actuator cable (9A825) aside.
Disconnect the vapor management valve (VMV) hose.
Disconnect the brake booster vacuum hose.
Disconnect the manifold vacuum connection.
Remove the PCV valve.
Position the EVR bracket aside.
Remove the two engine vacuum regulator (EVR) bracket stud bolts.
Position the EVR bracket aside.
Disconnect the following electrical connection: be careful not to break these, use proper technique.
Throttle position (TP) sensor electrical connector.
Remove the breather.
Remove the twelve bolts and the upper intake manifold.
REmove and discard the intake manifold upper gasket (9H486).
Installation
Install a new intake manifold upper gasket.
Note: Make sure to tighten the upper intake manifold bolts in two steps.
Position the upper intake manifold and tighten the upper intake manifold bolts in the sequence shown.

(Tighten the upper intake manifold bolts in the sequence shown. *** refer to the bottom

Install the breather.
Connect the following electrical connection:
Throttle position (TP) sensor electrical connector.
Install the EVR bracket.
Position the EVR bracket.
Install the two EVR bracket stud bolts.
Connect the manifold vacuum connection.
Install the PCV valve.
Connect the brake booster vacuum hose.
Connect the vapor management valve (VMV) hose.
Position the (A) accelerator cable and, if equipped, the (B) speed control actuator cable and install the (C) accelerator cable to bracket bolt and, if equipped, the (D) speed control actuator cable to bracket bolt.
Connect the (A) accelerator cable end and, if equipped, the (B) speed control actuator cable end.
Position the (A) accelerator control splash shield and install the three (B) accelerator control splash shield bolts.
Caution: Spark plug wires must be connected to the proper ignition coil terminal.
Note: Refer to the cylinder to coil tower relation indicated.
Install and connect the six spark plug wires.
Install the ground strap and bolts.
Connect the following ignition coil electrical connections.
Ignition coil electrical connector (A).
Radio ignition interference capacitor electrical connector (B).
Connect the idle air control (IAC) valve electrical connector.
Install the engine air cleaner outlet tube.


***
Install the 2 end capscrews to align the 2 halves of the manifold.
Tighten from the center most bolts to the outer most bolts. Tighten the bolts in two steps: a. Tighten the bolts on the first sequence to 5 Nm (44 inch lbs.). b. Tighten the bolts on the final sequence to 10 Nm (88 inch lbs.). Breaking one means starting over.