So I was under my car a few days ago to track down an exhaust leak.. between that and my idle problem, I was going nuts and HAD to fix one of them, and since the fixing the idle is almost impossible.......

anyway, i'm under the car, and as i'm looking around, i notice there's small a wiring harness by my transmission that's unplugged. i didn't pay a whole lot of attention to it, but i can tell you that it was about 3/4" round. it's been a while since i've touched O2 sensors, and even then I didnt pay attention to them (who cares what they look like, just plug them in, right?) but from what I remember, this is about what they looked like.

anyways, my rear 02 sensors have been disabled so they're not connected. do you guys think that's what the harness i found unplugged was?

while i'm at it....what sensors report vehicle speed to the ECU? Where are they located? I've noticed the WORST part of my idle problem deals DIRECTLY with vehicle speed. if i'm going 70 and throw it in neutral and coast to a stop (not touching the brakes at all), with my IAC restrictor it'll idle at 1700rpm until i come to a complete stop. and then i start counting, and in less than 3 seconds after stopping, it returns to idle. when i'm going 20, it does the same. idles high until i stop, then within 3 seconds, it quits.

i could understand if it was an automatic, since they can have 2 different idles set (one in park, one in gear, or something like that). but this is a 5 speed, and shouldn't have any control like that. my hanging idle is DEFINITELY related to speed, so VSS's are what i'm looking for next. any help would be great, thanks!

oh yeah, it's a 2000, 5 speed, 4.6L motor.

 

well can't tell you anything about your idle but it sound like the 3/4 round harness plug you explanied is for you backup lights plugs on the side of the trans and right behind it is the vss
(vehicle speed sensor)

 

same one came unpluged on me not an o2 sensor if its round its goes to your tranny just like Rantheman said have a friend tell you if your reverse light come on just dont run him over

 

i just turned the key on, engine off, and put it in reverse. reverse lights come on just fine. any other sensors back that direction? it's been raining here for the past couple days, so I haven't had a chance to get under it again yet.