Just fitted a whole new loom to my car that came from an xr3i efi car. Before i was using a fiesta rs turbo loom. I noticed that i have an extra plug on the xr3i loom. iv seen this before and it is a little white box that screws on top of the coil pack bracket. What is it? what does it do, and do i need it?

 

it's a capacitor. Put simply, it can help in keeping a clean rpm signal. Both terminals on the plug are actually joined together. The connection from the plug goes to coil +ve. It isn't essential.

 

Thanks for that, might as well put one on then when i find one.