HEGO orange wire grounds to manifold??
 

I was searching through past posts on this site for info. on HEGO trouble codes 41 & 91...I came across several posts that mentioned an orange wire in the engine compartment that is supposed to a ground wire (not sure why it would be orange?) for the O2 sensors. This turned on a light bulb in my head...because when I rebuilt my motor I had this 14 gauge orange wire coming out of the 10-pin connector's wiring harness right behind the upper manifold & T/B area...by the firewall of the engine compartment. At the time I had know idea what the wire was for...I didn't remember removing from anywhere when I pulled my stock motor out...so I just left it there hanging with the end wrapped in electrical tape. I've been driving my car for years now since the new motor and never thought anything about it. I only recently have been trying to tackle the codes that my EEC-IV is spitting out...because the performance of my upgrades seem to be up to par...except my mph could maybe be a little higher in the 1320' on motor. So do any of you know what orange wire I'm talking about? Or could one of you with an '89-'93 Mustang take a look at the wiring harness coming from the 10-pin connectors for an orange wire? Is it connected onto your manifold somewhere? I'd really appreciate a confirmation here. I'm pretty sure this wire should in fact be grounded to the manifold...but I wanted to make sure before I go and drive it. Don't want to melt something ya know?!

It should have a large eyelit on it and get attached to the back of the head.

Not having it connectd will only affect the EEC's ability to adjust fuel at part throttle conditions. The O2 sensors are not used at wide open throttle (WOT) and so would not affect your cars 1/4 mile performance if your car is a 87-93 car.