2002 4.0, what is this?

[Speedwagon]

Just noticed this on my 2002 4.0. Not sure what it goes to, as the wires disappear under the intake manifold.

 

[RonD]

That's the plug in for the Knock sensor, yes sensor is under the intake

You should clean up that wire, baking soda on wire and then add a little water, will clean off the corrosion, then seal with RTV or tape

You need the Knock sensor so you can run Regular gas(87 octane)

If you ever have intake off replace Knock Sensor

Picture of location here: https://www.explorerforum.com/forums/attachments/knocksensor-jpg.69257/

 

[Speedwagon]

Gotcha, thanks! Separating those wires seems to have improved the idling, as they seemed to be touching when I first noticed it

 

[RonD]

Yes, that could be, the knock sensor tells the computer(PCM) when to advance spark timing to avoid pre-ignition(ping/knock)

 

[Otis413]

I read that a failed knock sensor wont make the CEL come on, (that's why you should replace it when you have the chance) but you can test it by tapping on the block with a wrench at idle, if it's working the idle will stumble as the computer tries to adjust the timing due to the "knock".
Don't know if that's true, anyone tried it? I might give it a try tomorrow if it aint raining all day...