2002 S3 - missing on idle / slightly rough start up - lambda faults- please help!!!??

[jimbob442]

Hi any help really appreciated!!

I have a 2002 S3 BAM with 99k on it, the problem is that it drives fine but rough idle after about 20 seconds of first start - after the auto choke kinda idle, it starts fine but slight splutter on first 1-2 seconds, the only code coming up is the pre cat lambda is saying performance too low, could this cause these issues??

I have unplugged the MAF and problem stopped but then came back a minute later so I have took the mAF out of the equation!
I have checked all vac pipes under intake and replaced a couple and replaced the PCV valve as the old one was letting air through, I have checked all other pipe work and everything seems ok?!

Any help would be really appreciated as I'm at my wits end with this issue!! I'd take it to a VAG specialist but money is too tight at the moment for that!!

Thanks again
Jimbob

 

[kwistof]

Sounds very much like the pre cat lambda sensor. Mine has seen better days so I'm in the process of replacing it.

Got pretty much the same symptoms- works alright once warmed up, but first start every morning it's very rough- usually high revving at about 1200-1400 rpm. After a few miles at idle it goes back to about 800rpm. I got mine diagnosed on VCDS which highlighted the problem. Bit of a ****** to change I've been told so I'll be leaving it to the professionals to fit it! Lol

 

[jimbob442]

Thanks for the reply pal! Hoping that is the cause as I don't just wanna pump money into it and not get any better!! Mine is slightly different to what your saying tho as mine is the same rough missing on idle whether cold or warm, just a slightly rough idle to add to it!! These 1.8t seems like right niggly *******s!!!! Too many pipes and sensors!!

 

[jimbob442]

Sorry I meant slightly rough start up to add to it!!

 

[Broken Byzan]

Coil pack going down?

If it's over fueling due to a misfire it could be throwing the CAT code

 

[jimbob442]

Coil pack are all new from recall, also tried 2 off Sandip and not coil packs it's a multiple misfire but no codes for the misfire just lambda sensors?! I wouldn't have thought a lambda would cause this issue or would it??!!
Thanks for the replies lads! What do you mean by CAT code, Could a ****** CAT cause it?!

 

[S3SYD]

Do a boost leak test mate
As boost and vacuum leaks cause that issues
Plus mines is doing that at the moment just like yours
done the boost leak test and found a few leaks but haven't got round to fixing them

 

[jimbob442]

Do a boost leak test mate
As boost and vacuum leaks cause that issues
Plus mines is doing that at the moment just like yours
done the boost leak test and found a few leaks but haven't got round to fixing them

Thanks for the reply mate, is it possible to do a boost leak test myself or will I need to take it somewhere?! Your symptoms the exact same?? If so its good to know I'm not the only one pullin my hair out!! How dd you do a leak test or how much would it cost at a garage?? Thanks pal

 

[s33nyboy12]

Technically you could do it yourself, however without the dye I think they use you wouldn't be able to pinpoint the leak/s

Silicone pipe, bung, foot pump, 1/4 inch pressure gauge you could probably do it....... However no dye, and that stuff not cheap

 

[<tuffty/>]

What was the exact fault code/description you got for the lambda?

If the lambda has a problem then this will affect fuelling and subsequently idle/part throttle/cruise and WOT...

Assuming the lambda probe is faulty then first thing is to fit a new one and then see if you have further problems... you are going to be chasing your tail if you haven't fixed a known issue... these engines need all the sensors in place and working to even stand a chance of running as they should... sort that out first then take it from there..

<tuffty/>

 

[<tuffty/>]

Most good garages should have a smoke tester... they are around 600/700 quid to buy so not a DIY solution... we typically smoke test most cars that come in for remaps these days as there are very few that don't have a leak somewhere..

<tuffty/>

 

[jimbob442]

Most good garages should have a smoke tester... they are around 600/700 quid to buy so not a DIY solution... we typically smoke test most cars that come in for remaps these days as there are very few that don't have a leak somewhere..

<tuffty/>

Cheers for that tuffty, will get a new lambda and go from there! Just thought buying a VAG car would be reliable but not seeing the reliability at the moment!! Then for a smoke test I think!!l

 

[<tuffty/>]

Cheers for that tuffty, will get a new lambda and go from there! Just thought buying a VAG car would be reliable but not seeing the reliability at the moment!! Then for a smoke test I think!!l

Generally speaking they are but... they are also old cars and they all suffer from the same issues... worn pipes, old sensors etc... they all suffer the same, VW, Seat, Audi and Skoda... same engine, same issues...

Once sorted though all should be good... you also have to remember that a previous owner may not have noticed/cared as much as you about keeping the car serviced or whatever... see it far too much now... as the cars become more affordable then they change hands more quickly... especially S3's.....

Common issues are pipes under the inlet manifold (essentially anything thats rubber/plastic) are known to split from oil degradation, clips lose tension over time and you get leaks at the intercoolers as the header tanks are plastic too... the orange turbo to charge pipe hose is known to split (100k next to a very hot thing will do that...)

<tuffty/>

 

[jimbob442]

What was the exact fault code/description you got for the lambda?

If the lambda has a problem then this will affect fuelling and subsequently idle/part throttle/cruise and WOT...

Assuming the lambda probe is faulty then first thing is to fit a new one and then see if you have further problems... you are going to be chasing your tail if you haven't fixed a known issue... these engines need all the sensors in place and working to even stand a chance of running as they should... sort that out first then take it from there..

<tuffty/>

Just an update... I got a bosch lambda (Pre-cat) and the car drives fine now, big difference, although still missing like a tw*t on idle!! Lumpy and stuttering, checked all vac pipes / boost pipes, replaced pcv and a few pipes and the funny shaped vacuum suction pump thing... Still no joy!!

PLEASE HELP!!!!!! Could it be MAF? If I unplug it sometimes stops the misfire but not always, I've tried this a few times now!!!!

At my wits end!!!!!

Thanks guys