Emission Control System warning
 

I've looked in various sections and can't find any reference so hopefully this is the right section to post in.

Last night I drove the S8 for the first time in five days and noticed it was "lumpy" when moving off from standstill and the warning lamp was flashing. I pulled over and turned it off for 30 seconds or so, restarted and the lamp stayed off and the car drove fine.

Came out early this morning to use it and although the car drove fine the lamp stayed on constantly. I drove steadily for the two miles of my journey and parked up, tried again a few hours later after my visit was over and same thing occurred, the lamp was lit constantly but the car drove smoothly.

The manual states to take it to a qualified workshop as soon as possible, which I will do of course but I'm wondering what sort of thing would have caused it to be activated. Has the short period of lumpy running yesterday caused the fault which now needs clearing, or is this an indication of something more serious? I'm aware of the potential damage to the cat(s) as indicated by the manual so will only take it the three miles to the garage, or is this a case where I should leave the car where it is and ask someone with the correct diagnostics to come to me?

Any advice would be much appreciated

Ron

Do you have vcds to do a scan, as you know the control systems on these cars are so complicated it could be a number of different things and we can only start making educated guesses with a scan from the car

Unfortunately I don't Del and I don't recall seeing anyone on the VCDS register from this area. My local independent will do a scan on it for me on Monday and I'll see what happens then.

As you say, they're very complex and I'm sure it's linked to the lumpy running last night. I pulled away earlier than usual last night (before the revs had dropped after the cold start) and that's something I've never done before, I'm hoping the cause and fix are both simple.

Thanks for the swift response +++

I don't think the pulling away before the idle has settled is the problem as I do it in mine all the time and it does feel lumpy till the sai has got the cats up to temp.

It does sound very similar to a coil pack failing as thats the exact symptoms I had on a 3 series bmw.

It was intermittent and would throw the cel light on when it misbehaved but when it was ok the light would clear its self after a while.

Hopefully it will be as easy as that for you to get sorted, will wait to see what the mechanic says when he scans it.

Fingers crossed for you.

Lumpy running was most likely because one or several cylinders was not running properly, it could be due to incorrect air/fuel mixture or ignition issue. Probably coil pack or spark plug but cannot tell for sure without a scan and further investigation.

Cheers Gents, I appreciate it's all speculation until I can get her scanned but at least I'm not miles from home. The plugs are recent as Ian changed them during his ownership but the scan will hopefully clarify the cause and solution.

Great input, I'll keep you updated +++

Defo needs a scan to tell for sure. The V10 is a lumpy engine when cold at the best of times - my S6 is exactly the same. Being stood for 5 days isnt a problem, so you're looking at a little bit of something its unhappy with, but as it drives ok, it seems unlikely its anything too serious....

Thanks Ian, I've got a scan arranged for tomorrow afternoon, so hopefully I'll know better after that. It drove fine after the initial problem occurred so I'm hoping its nothing serious.

I'll be paying close attention when they plug it in and check for fault codes

It'll be getting a good run out to Northampton in a few weeks, I'll make sure I give it a bit of work to do :cool:

Not looking good I'm afraid, take your pick from coil packs, sticking valves or timing chain slipped, or all three even.

Booked in for recovery from my independent next week and transferring to a local(ish) VAG specialist for further investigation :(

So you paid for someone to guess? Did you not get a scan from the car?