Secondary Air Injection System
 

Been having problems recently, VAG-COM pulls up the following:-

17831 - Secondary Air Injection System; Bank 1: Insufficient Flow P1423 - 35-00

17819 - Secondary Air Injection System; Bank 2: Insufficient Flow P1411 - 35-00

That was after I noticed the engine light on a few days back.

Then this morning on my way back south, just cruising along at 75, suddenly all power cut, ABS light on, EPC light on and for the next 60 miles it wouldn't accelerate up any form of incline, only on declines and not with full power.

Got to work, checked it out with VAG-COM, same code 17831 amongst others from the ABS saying problem from throttle position sensor. I think the TPS and ABS problems came as a result of driving after the 17831/17819 codes.

Reading up on the codes at the Ross-Tech wiki, does anybody know where to look for this secondary air injection pump and the valves associated with it, as I'll have to check the pipes over to start with - this is the problem that has been causing the little hesitation changing gear and at about 3500-4000rpm under load I think.

Any help finding the pump/valves/pipes much appreciated +++

Ah, found some diagrams on VagCat, no worries chaps +++

How odd....

The secondary air pump is sat in the bottom of the airbox at the front of the engine bay...

Its fair to say that they are a common-ish fault.

Both my S8 and RS6 delvoped faults in the system.

I had the pump, and one of the valves fail, however I would say that they cars drove normally whilst the faults were present....

This severe loss of power, and involvment of the ABS system suggests theres more going on here than first meets the eye...

I suspect the engine ECU may have turned off the ABS/TCS etc, but for that then it must be thinking its got something more major at fault - I guess if there were a problem with the throttle position sensor, this would be a fairly major concern causing the ECU to intentionally not to respond to full power requests....

I replaced the throttle position sensor on my S8 and made a massive difference to the drive.

A problem on the slightly higher mileage cars is that an engine breather chucks oil through the throttle body and gums it up.

I removed the throttle body (Quite straightforward without removing the inlet) and stripped it and cleaned it. I also relocated the engine breather pipe to stop it being gummed up in the future.

Car drove miles better afterwards.

Well when the engine light came on, I was just driving gently to the shops for lunch, probably no more than 45mph. Nothing happened, I just happened to notice the light was on, so I checked it with VAG-COM and only got the two air injection faults. Thought nothing of it at the time, no running problems or anything, so cleared the DTCs and everything has been fine.

Drove home that night, no problems. Headed north on friday, no problems again. Drove for about 110 miles this morning, no problems at all then suddenly this loss of power. I was in cruise control, 75mph.

The only thing I can think is that the fault caused a hiccup in power which triggered the ABS which perhaps misread the throttle position due to it being in cruise? Dunno, scratching my head, but this is the fault read out from this morning and the engine had not been switched off since the fault occurred:-

Engine:

17831 - Secondary Air Injection System; Bank 1: Insufficient Flow P1423...

18047 - Accelerator Position Sensor 1/2 (G79/G185): Implausible Signal Readiness: 0010 1101

ABS Brakes:

18264 - Throttle Potentiometer (G69): Error Message from ECU P1856 - 35-00

I'm pretty sure this is connected to the very intermittent problem that occurs at about 3500 to 4000rpm under load when there's a slight hiccup, almost like it's thinking of changing down a gear or something. I've been driving it like a grandma for a few weeks now, frightened something else expensive is gonna break on this gearbox, but now I'm starting to think the real problem is revealing itself.

Once these problems are ironed out and it's had a bit of TLC on a few scratches and chips, I think I'll be parting with it anyway as I (and my wallet) have had quite enough of 8 ownership :-(

Insufficient flow on my D3 related to a split vacuum pipe. Replaced and sorted.

Definetely check them.

Cheers Doc & Ian BTW, I'll start having a look around the pipes first - I found PaulW's posts about chasing these pipes and doing the VAG-COM output tests, so I'll do the easy stuff first and then if there's still a problem I'll have a go at the output tests and report back.

Found the problem(s).

Part number 4 in the pic, like a little rod-operated bellows thingy, the rod's mounting clip on the rubber bellows has snapped. Any ideas where the hell I'll get one of these from?

Also pipes are crumbling in my fingers, so I'll have a bit of a replacing session with it all.

Going to look at a new motor tomorrow... more details soon - my S8 will be up for sale soon, once these last few niggles have been sorted.

http://forum.a8parts.co.uk/attachmen...3&d=1241173654

A8Parts will have one and be able to supply a set on non-crumbling hoses.

Here

Not sure if the guys at A8P will be ok with this information - please remove if not acceptable, just trying to help others if they get stuck like I have (I'm towing my caravan back north in a week's time so this is getting rather urgent). +++

Well, interesting development here - the guys at A8P didn't have any unfortunately, so I went on the hunt and found some interesting things for anyone who has this particular problem.

Rang Audi Amersham, spoke to parts, gave him the part number off vagcat (077198327A - repair kit for adjuster), he gave me a price, I fell off my chair... :Confused:

Asked him what the kit contained, he asked a technician who said there were two bellows things and some linkages, £147.80 inc. I said my thankyou's and went online to hunt.

First of all I put the Audi part number into google, found this http://forums.audiworld.com/showthread.php?p=15582059 which sort of explains pretty much what I'm experiencing - lack of power when it hits a certain point in the rev range.

The bellows units are made by Hella (part no. 004 538), so I put that into google and found these http://cgi.ebay.com/ebaymotors/1985-...31010008r16443

Hmm, very interesting. Needless to say, I did some more hunting and tracked down the exact same part as the audi one on ebay albeit without the linkage bar for less than 20% of the price audi quoted. Range Rovers use it on the cruise control too (part no. ETC7150). I'm happy this repair for once hasn't cost me £100+ ;)

I'll update if the part works when it arrives.

The older A8/S8's have the bellow on the cruise control too. Might be worth an option?