Festival of warning lights and beeping!

There was (as someone suggested earlier) an intermittent fault with the yaw sensor, which I couldn't detect using my gadget.
The electronics involved in modern cars are complex and difficult to fathom, particularly for those of us who developed their mechanical skills in an earlier era.

I'd not be investigating that misfire further ahead of obtaining and fitting a replacement yaw sensor.
 
Trust what the VCDS scan has flagged up. Now you have a known starting point with only current faults. The vacuum leak may be from one of the small hoses that has split or cracked or even loose on its fitting. The sensors are capable of noticing small changes so although the engine is producing vacuum the sensor may not be receiving the correct vacuum or it is not able to compare it correctly with either a preset value or static pressure. Remember some actuators and valves are only in use during specific times when the engine is either started, cold, idling, above idle, shut down etc so the leak may not be obvious. If you have your owns VCDS you can check out your own progress and report back with what you find Good or bad.
 
Replace the throttle body and then do a trottle adaptation and you should get rid of these fault codes:

  • 17961 - altitude sensor signal / intake manifold pressure implausible ratio
  • 17912 - Air intake system leak detected
  • 01314 - Engine control module (in the ABS section on my scanner)

Had the same problem with my AUA engine and cleaning the throttle body didn’t solve the problem nor did a throttle adaptation. Took a lot of effort before I realised that the throttle body was defect even though the adaptation passed without any errors in VCDS.
 
Replace the throttle body and then do a trottle adaptation and you should get rid of these fault codes:

  • 17961 - altitude sensor signal / intake manifold pressure implausible ratio
  • 17912 - Air intake system leak detected
  • 01314 - Engine control module (in the ABS section on my scanner)

Had the same problem with my AUA engine and cleaning the throttle body didn’t solve the problem nor did a throttle adaptation. Took a lot of effort before I realised that the throttle body was defect even though the adaptation passed without any errors in VCDS.

I’ve also had to do this on a bby


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Forgive my ignorance, but what is a throttle adaption?
in VCDS there is an option for this, though after replacing it on mine it picked up and ran fine after a couple of start/stops, could have just gotten lucky.

obdeleven has this as well which was what I used. no affiliation just handy as it does some of the basic bits from a phone app.
 
If you haven’t done it start with a TBA to see if it solves the problem. If not then replace the throttle body and then do a new adaptation.
 
My two cents: For 'adaption' read 'recalibration'.

The ECUs receive measured voltages from various sensors. Those sensors can drift over time, be replaced, etc. and the returned voltages are outside of what it's expecting. So you tell it to accept a different range and to go off and find out what that is, or help it to find out what it is.

I recently ran an adaption for my TT soft top as it thought the flaps weren't opening or closing fully from the returned voltages, can't recall which just the usual panic when the soft top stops working :)
 
if you check the part number i might have one actually - though i think mine ends with a different letter at end (M instead of N or something) as it is off a polo. not sure if it is actually different or just newer revision.
 
Hi all,

Thought I'd better give an update because.... I've fixed it! Or at least got things running much, much better.

So, embarrassingly, it turns out the reported air leak was in fact an air leak. Who'd have guessed? Not me, clearly. However, it was a tricky b****r so I think I can be forgiven for having missed it.

It was leaking between the two halves of throttle body assembly (i.e. between the throttle body and the other bit that the EGR and vacuum take off attach to), and possibly also between that and the manifold, though I think probably not.

Basically, at some point someone had used silicon to seal the two parts together, and I didn't really stop to question that. I guess when I was cleaning it things got disturbed, or maybe some of the gunwash I used for cleaning got into the silicon, and it started to leak.

Of course, when I pressed my hand down onto the open throttle body to test for a leak and found none, I was pressing everything together and probably helping to seal it up temporarily, and disguising the leak! Idiot.

Anyway, I only discovered this by accident when, in frustration I decided to take it all off again for another look and realised that there were strings of silicon hanging off when I pulled them apart.

I cleaned everything until it shone, and then put back the alloy gasket with a ring of fresh silicon either side. The seal with the manifold looks good to me - it's soft and springy - but I'm not sure how I can check it's fine other than to spend another £8 on a fresh one.

So, some more questions....
  • Does the metal gasket between those two parts normally get installed with silicon either side, or it it some sort of single-use crushable gasket?
  • Is there a torque value for the throttle body bolts?
I still have a misfire on cylinder 2 if I let it idle, but quite honestly this feels like a huge step forward as the car is quicker and nicer to drive than at any time since buying it.

Thanks so much to everyone who has offered help and advice so far!
 
Who would have thought! Congrats on getting to the bottom of it.

few I have seen only had the metal gasket and no silicone goop on there.

Torque value was 10nm from memory.
 
So, some more questions....
  • Does the metal gasket between those two parts normally get installed with silicon either side, or it it some sort of single-use crushable gasket?
  • Is there a torque value for the throttle body bolts?
The gaskets on the throttle body and EGR valve are single use metal crush gaskets. They aren't meant to be re-used but in the past they obviously have been and as they had not functioned correctly on re-use, the extra sealant was a bodge the make the old gaskets work.
 
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