Audi A4 Auto ALT 2.0 2006
 

I recently purchased an A4 that has a rough Idle.

I replaced the Breather Valve as there was no Valve in it.
I replaced the Breather line Pipe/Cup just below it as the pipe was missing a huge section.
I Replaced Some of the pipes going to the Break Boost (The T junction and One way Valve)
Installed a Missing Plastic C Clip to hold the Breathe Valve
Reset the fault codes (But there weren't any)
And still idled like crap.

So a friend came round and disconnected the MAF Sensor and car idled fine. (He said it put it into default mode) and recommended it change that.

I then installed a MAF Sensor (OEM) and housing. And reset the fault code generated by not connecting the MAF

And its only marginally better. (Actually It does seem to sound better and drive a little smoother) (But still randomly coughs and stall)

So I went on the hunt for possible vacuum leeks.

I noticed that there was a 3 pin Gray connector unplugged on the right hand side of the engine under the water container. following the cable it was attached to a crank sensor. This sensor was dangling in the void not attached to anything. I quickly found the hole it was meant to plug into.
and pushed it in and got a grinding noise. (Turns out that Audi made it so you need to put a spacer in first). So I stopped!!!!

How is the car running without the sensor in???

Where does the electrical end connector go to?

I contacted a friend who does MOT's etc. and he said without that sensor the car should not run at all.

So I went online to do some research.
https://cimg8.ibsrv.net/gimg/www.aud...274a3bc3b1.jpg

The car is an AUTO and according to the AUDI Parts guide there is a 20pin Auto transmission control wire in the place where the 3pin Crank Connector should be.

Has someone added this crank sensor by mistake at some point and it isn't actually for this car. (Which is odd as the hole and fixing point are open/empty/present)

If the crank sensor is not needed any ideas on what else to try with the bad idle....

Thanks.

Rob