Its a 98 4.6l randomly overheated and threw code p1299. Changed ect sensor and thermostat. Pump works and fan works. It runs but very poorly, like its missing all over the place. No water in the oil or bubbles in the coolant no white smoke either. I found some random plug which I think may be the culprit so....

Can someone please help identify where this plug goes? Its on the driver side leaving the harness that plugs into the coil pack. Its in conjunction with what looks like an oil pressure sensor or oil level sensor, right on the bottom of the block.



Any suggestions or info are greatly appreciated.

 

If you still have the 1299 code it won't run very well because it puts the PCM in limp mode that takes cylinders out of service on a rotating basis.
Be sure all air is out of the cooling system.
As to the plug, you have to look around in the area the harness will reach without excess pulling or tension on the harness.
Can't tell from the photos where in the engine bay it is.
Most people who photo, do it to close in and lose area reference detail.

Good luck.