S3 BAM problems - tearing my hair out


Registered User
Evening all.

Just taking time out from banging my head against the wall.
My S3 hasn't been behaving for a couple of weeks now - finally got chance today to have a decent look.

Basically the power is down (boosting, but air is being dumped as I ask for more boost)
While accelerating, getting a couple of misfires in 4th, 5th & 6th gears
In any gear, I struggle to reach 5k revs
Coolant temp gauge sitting around 70/75 ... (normally steady 90, or drops a bit at high speed/low revs)

I found a small leak on one of the vac lines, so replaced the pipe.
Changed the spark plugs - plugs 1 & 2 were covered in oil (on plug 1, just the tip of the plug was visible above the oil !). Cleaned out the holes and put new plugs in.

MPG seems fine, averaging around 31/32 combined.

Took it for a spin, still exactly the same. Will get it on VagCom at the weekend.
Any ideas in the mean time ?


Registered User
Just been having a search through some old threads ...

Could it be possible that all my running problems could be down to a dodgy thermostat ? The temp gauge never reaches 90, and every answer to this symptom suggests the stat. Also, regarding the oil around the plugs - well seems I might need to renew the seals under the rocker cover + new rocker cover gasket.

Can the thermostat be refurbed - I mean - If its sticking, can it just be free'd off and put back in ? Might need a new seal for it though ?

Am I barkin up the wrong tree ?


Audi-sports own special child.
No, new one mate, their only about £20, also change the temp sender for the sake of a couple more quid then it rules out both.


Registered User
It will be one or the other ..temp guage should be at 90c when at normal running temp.Engine coolant temp needs to be hotter than 80c to be at normal running temp under 80c youre on cold start up.
Check vagcom measuring blocks for temp in engine ecu then compare against dash panel ecu if both readings are the same you can rule out temp sender... more likely to be thermostat. As above both are cheap to replace

Optimum Tuning

Make sure you check vac line to fuel regulator on fuel rail Mine dropped off when driving hard and wouldnt go past 5k,misfiring and cutting boost aswell.Worth a check!;)

steve bain

Registered User
thermostats are only £9 from GSF if it helps. mine won't get up to 90 either so its a job for this weekend. bet it rains!


1st gear
can't see the stat or sensor stopping it going past 5k, probably 2 faults 1 being the stat or sensor and 2nd probably coilpacks


Registered User
Thanks for the ideas guys, appreciate it.

Well, the mis-fire has gone. I pulled out coilpacks 1 & 2 to check for oil, and both holes were spotless. Acceleration feels a lot smoother, but the power is still way down. I noticed all the coil packs were in decent looking condition, and looking inside at the connection piece, all were a goldish colour. I cleaned them best I could with some carb cleaner and some cotton buds. The connector on pack 2 looked a bit dodgy too, might see if I can source a new plug from somewhere.

As for the temps - well - the needle doesn't seem to move off 72 degrees regardless how long or hard I drive it. On the night shift this week so will get the thermostat changed at the weekend. I'll take the advice and change the CTS at the same time.
If the stat has gone then you're unlikely to get it warm with spritied driving as it will stick open meaning you're coolant system will be working overtime when you're giving it beans. When mine went it would only hit 90 degrees when it was in standing traffic (as the rad wasn't being air cooled).

Re coilpacks, my failed ones looked no different to the new ones in terms of external condition, it was the electrics inside that were goosed. Have you vagcom scanned it? That should identify a misfire in the indivdual cylinder(s) which have faulty coils.


Registered User
Haven't scanned it yet - another job for the weekend !

Just going back over an earlier point .... if for example, the only symptom was the dodgy/failed thermostat ... realistically what adverse effects would this have on engine performance.

and ...

On cold start up in the past, I know my car was very nippy and seemingly had all its power available, so in theory, I should be feeling the same response from the engine for at least the first few minutes after a cold start ? Thoughts ?
Adverse effects of a faulty stat are that the engine will continue to run on cold cycle as it won't get up to standard operating temp. The only noticeable effects on my car were that the MPG suffered slightly. There could have been mild performance effects but they weren't noticeable when driving.

Your car shouldn't feel faster when it's cold unless you have some other unrelated issues, also I don't think it's advisable to be giving it full beans until it's warmed up a bit!


"Stick a V8 in it!"
Staff member
VCDS Map User
IF its a faulty CTS rather than the stat it may cause those symptoms.

CTS tells the ECU the engines temperature, if its always sending "Cold" even when its hot, its going to run like crap.

Do the stat first, as even if its not completely stuff its probably worn anyway. If that doesnt cure it, drop a new (Genuine) CTS in there.


Registered User
Ok then, a little progress.

Firstly, scanned the fault codes - got 8 altogether.

16711 Knock Sensor 1 Signal too low
16500 Engine Coolant temp sensor implausible signal
17956 Boost pressure control valve (N75) open circuit
17705 Pressure drop between turbo & throttle body (check DV !)
17947 Clutch pedal switch (F36) implausible signal
18010 Power supply B+ voltage too low
17695 N249 open circuit / intermittent
16396 Bank 1 Camshaft A (intake) advance setpoint not reached (over retarded)

Well, the coolant sensor, N75 and N249 faults were probably because I unplugged them whilst checking them out.
Clutch pedal sensor would be from when I changed it 4 months ago (pain in the **** job to do)
Power supply when I dropped the connections off the battery

Which leaves 3 faults ... knock sensor / pressure drop / camshaft setpoint.

So, I cleared the codes. Went for a lengthy drive - rescanned - only the Knock sensor one re-appeared. Checked the plug connector to it, seemed like one of the wire joints was bad, so remade it and plugged in. Cleared codes again, went for a drive, and all is clear !

The other odd thing is that driving around with my climate control switched off has now caused my coolant temperature to reach and sit at 90c as normal. Turning it on Hi temp with full fans makes it drop to 75 ?!!

Now I have nothing coming up on DTS, the car seems a lot better to drive but still down on power, and still the same whooshing/recirculating air noise as before. I only have the unregistered version of VCDS, but could still manage to log block 002 to check out the air mass. Didn't want to push too hard, but in 3rd gear at 4000 revs it maxed out at 149 g/s. IS this low ? I read another thread with a post from Welly advising to log blocks 020 and 115 too. I can log block 020 but not 115. Is this a low g/s reading ? What could it suggest ?

Thanks in advance...


Registered User
just a quickie ...

... managed to log a couple of blocks on way home from work this morning. Could only log blocks 002 and 020 as Im using shareware version of VCDS. Not really sure what Im looking at ... would anyone be willing to take an educated look for me ? 3rd and 4th gear from 3000 up to 5000 rpm. Didn't fancy going any harder :S



Registered User
Whats the best way to post up an excel/open office spreadsheet ? Havin trouble here !


Registered User
Thanks Dave .. will have to register this copy of VCDS, might be worth its weight in gold before long. Block 115 is requested boost versus actual boost right ?


Registered User
Couple more symptoms to add to the list, they cropped up over the last couple of days ...

Temp gauge issue - seems temp gauge stay very low (70/75) when climate control is switched on (and on heat) - turn it off and the temp gauge SLOWLY moves toward 90, but never quite reaches it (85 ish)

Boost issue - in 2nd and 3rd gears, when accelerating I get this sound - like a "farting" noise, or could be even a buzzing noise - hard to tell if its around the boost pipes or whether its from the exhaust mani - anyway it only happens when revving from 1600 up to about 2100, then goes away. Still low on power, although my MAF readings don't look too bad at all !


"Stick a V8 in it!"
Staff member
VCDS Map User
Change the stat.

With the AC on it fires up the electric fans up front, meaning more air forced thru the radiator. The stat should be closing down the water flow, and its not.