Hi
Been working on the engine bay today cleaning things up, the car runs really well but i’ve noticed a plug and socket that’s not connected. If you look under the bonnet along the rocker cover right at the back slightly to the right near the bulkhead the plug has 4 pins on it. Any help would be much appreciated, just to know what it is and should it be left unplugged. For refference my car is a 95 1.8 Eunos.
Thanks
Hi and welcome,
Only thing I can think of is the auxcilliary power socket but thats further foward see picture.
Thanks Air_1 no it’s deffinately on top of the rocker cover near where all the plug leads meet at the back … I plugged it in and the car still started but didn’t have time to take it for a blast. Not sure wether i should run it connected as been ok disconnected.
(I love that smiley 
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Can you trace the wiring that goes down towards the exhaust side? I’m wondering if you might have a disconnected O2 sensor. Can you see the colors of the wires that go into the plug/socket, these might help identify things.
Hi I’ve been trying to upload a photo without much luck, the picture is in my photo album i’ll keep trying. The plug has always been disconected since I bought the car, what would happen if I reconnected the plug presuming it’s the 02 sensor.
Thanks again to all
I agree it sounds like the O2 (lambda) sensor.
If it’s unplugged, your car’s ECU doesn’t have any feedback from the exhaust gases to tell it how lean or rich it’s running, so it’ll run extra-rich just to be on the safe side. That means you’ll waste a lot of petrol (down to somewhere in the low 20’s of mpg typically). It’s also unlikely to pass MOT emissions like that.
If you reconnect it, then - assuming the sensor actually works and assuming it isn’t fouled with soot - your mpg should improve to somewhere closer to 28-30 mpg (depending on your driving style and typical journey).
I’ll give it a go, off to Manchester tomorrow should se a difference in consumption if it is the 02.
Thanks to all who replied
