9N3 Engine disconnected wire

[KazamPolo]

Hi, I'm new here and completely clueless about cars. I recently bought a secondhand Polo - I think I'm right in saying it's a 9N3 - I would've called it a MkIV facelift base don Wikipedia... anyway we were looking under the bonnet and found this disconnected wire tucked away which I'm very concerned about! I have already driven it and it's been running fine. I've looked and for the life of me can't see anywhere that it would connect to! I would really appreciate if anyone could tell me what it is supposed to be for and how dangerous it might be... pictures attached. I will try and provide any other information you need if this isn't enough. Thank you!

Liz

[alexperkins]

That's the injector loom. What engine type is it?

[Jessesam]

That could be knock sensor connector from back of engine block

[KazamPolo]

Thanks for the responses!

What engine type is it?

It's a 1.2... is that what you mean? What would the implication of it being connected to nothing be?

That could be knock sensor connector from back of engine block

Erp, from looking that up it sounds important... there doesn't seem to be anything to connect it back onto, would that mean said sensor is missing?

[RUM4MO]

Yes, I'm guessing we all know it is a 1.2 3 cylinder - but the version will by B**, it is the "**" that could help - that info will be on the build data sheet in the spare wheel well side or boot area.

[KazamPolo]

the version will by B**, it is the "**" that could help

I think that would be 'BBM'

Major update though - with some careful mirror/torch work I managed to find where it connects and have reconnected it. I went around the block and nothing seems to be any different but I feel happier that it's not just loose... I would still be intrigued to know what it is though and whether there is any reason someone would have disconnected it on purpose - I'm working with the theory that it was accidentally pulled out and no one realised as originally it wasn't at all obvious that it was that way.

[RUM4MO]

BBM sounds okay, I think that the "knock sensor" is just a rugged microphone that is bolted lightly on to the cylinder head and its task is to listen for the onset of pinking or knocking which is caused by poor fuel quality and/or air leaks etc. I'm just surprised that VW group have not built in a function that "knows" when that lead has fallen off! Of course, you would not normally notice any difference in how the car runs/drives if there was no knocking - which there should not be, but some engine types have a form of dynamic engine timing that constantly changes the timing up to the point that knocking is just starting to happen - then backing the timing off again - etc , etc, maybe not in this model of engine though.

Edit:- still a bit annoying to find a disconnected lead on a car you have just bought thought?

[KazamPolo]

Oh definitely annoying - but nowhere near as annoying as what has just happened. I've had to have the AA tow me home. The coolant level started dropping dramatically and it looks as though the head gasket has failed, possibly due to a bad repair job in the past. No record of this being done but the AA guy said he can tell the engine's been opened before.

I'm taking it back to where I bought it tomorrow to see what happens, I have a warrantee.. but altogether not what I was hoping for with my new car

I also showed him where I'd reconnected the wire and he said it's actually the oil sensor - for detected the quality of the oil or something? He used to work for VW which was helpful but he didn't seem impressed overall with what he was seeing. I could've done with him being there when I bought it.

[RUM4MO]

Well that is terrible, lucky you still have some warranty life left, if you are in the AA you can, I think/thought, get them to check a car over before you buy it if it has not already had the AA Approved guarantee on it already - but as always, these guarantees come at a price though this inconvenience will also come at a price to you in terms of "no car" - bum, bum, bum, good luck!

Edit:- I've never used the AA to check a used car - so that was just a bit of advice given too late, sorry!