ABY cutoff-ing

[max_s2]

Hello.

Can someone tell me what should I look for to repair my engine? :/

Some weeks ago my ABY started to cut-off/twitch after some time when engine is hot. On cold engine no problems, nothing cutoffss. First I checked sparkplugs - on 1, 2 cyl. they where totaly black, on the rest 3, 4, 5 cyl. everything was ok - brown as it should be.
Decided to change all the sparkplugs with brand new F5DPOR. Ok, byued, now it's time to change. Removed old sparkplugs and here the whole thing started.. - all sparkplugs where black. Seems like my engine has overfuel. Cutoffs also didnt go away. I gues that overboost also doesnt work for some reason because it boosts up to 0.8bar only.

The third thing after cutoffing and overfueled sparkplugs that dont let me sleep well at nights is that my onboard computer shows too big fuel consumption. 90-100km/h average it shows not less than 9.0l/100. I've seen on the internet that cruising around 90km/h there should be around 7.5l/100km.

Some days ago connected to Vag-Com, here are the results:
00513 - Engine Speed Sensor (G28)
27-10 - Implausible Signal - Intermittent

Please give me some advices to look for! Thank you.

[PeteRR]

I'd start having a good check over all the intake hoses for any holes, splits or even a loose clamp that may have introduced an air leak.

Also, the Speed Sensor code will come up when the codes are pulled with the engine not running.

[max_s2]

I gues that this G28 is not that one witch apears when engine not running. Car was tested on running engine.

Air leak can couse engine overfuel?

And as I mentioned cut offs are only when engine is hot (around 1300rpm and above).

[S2central.net]

Air leak or bad MAF can cause overfuelling - simply because the ECU injects more fuel than is required for the amount of air which actually got inside the engine.

Also you might have faulty fuel pressure regulator, but that is rather rare.

Other possibility is faulty lambda sensor - these need to be replaced every 60k miles.

[PeteRR]

You might want to clear those codes and test again, just in case it's an old code.

An air leak could cause a rich mixture, poor running and excessive fuel consumption. Particulary check downstream of the turbo too if you have cutting out.
And Paul's right of course, the MAF is another possible culprit.

[max_s2]

Replaced MAF form my 3B - nothing changed, replaced back to orig.

Before cutoffs show up, fuel consumption already was like I wrote above - not less than 9.0l/100, also after and before lambda was replaced.

Maybe the fuel pressure regulator? How to check it?

Btw, the cut-offs on 1, 2, 3 gears are rather hard.

[220bhp]

If the tps is faulty it can cause over fueling and cut of. you can check it buy operating the throttle buy hand and listen for a click, if it doesnt click it is faulty.Do this from under the bonnet with the engine of.In case you dont know,the tps is the little black box on the side of the throttle body,you can also check it with a multimeter's, do a search on hear to tell you how.

[max_s2]

The code apeared when the cut-offing started. I cleared this fault. After 15min I'll test with vag-com again.

Where should I look for air leaks under the hood?

You might want to clear those codes and test again, just in case it's an old code.

An air leak could cause a rich mixture, poor running and excessive fuel consumption. Particulary check downstream of the turbo too if you have cutting out.

[S2central.net]

If you are getting cut-outs then its more like an air leak... Check ALL the hoses from airbox - turbo - intercooler - throttle body. You really need a pressure test kit to do thos properly.

[PeteRR]

You want to check all the large diameter rubber air hoses, to and from the intercooler, turbo and inlet manifold/throttle housing. (It's also well worth checking all the smalll diameter vacuum hoses too.)

If you're getting cutting out under acceleration it could point to a boost/air leak or possibly coil packs.
Does the engine cut-out completely, or 'stumble' but remain running?

[max_s2]

Checked with Vag-Com - no faults. So far everything seems ok.
Engine remains running, cutoffs are on acceleration yes and only when engine is up to its working temp. - around 90c.
OK, I'll check hoses, thanks to all for ideas!

[QuattroFever]

my ABY has been suffering with this problem for ages!

I've done a boost leak test and no probs.

Plugs are black.

I've vented the breather to atmos. The black valve was leaking boost from a tiny square hole in it, aven't got round to replacing it yet.

I've found that using an octane booster stops it??? almost like it's timing related like it's sensing knock or something and going into limp mode and wont boost above about 5psi???

[UrS4boy]

I think your problem is related to the crankcase ventilation system.

Suggest you read this:

http://forums.audiworld.com/s4s6/msgs/133287.phtml

and then repair the system so it operates properly.

Dave F.

[QuattroFever]

i've vented the breather to atmos and plugged the other open end. So breather system should be out of the equation and it still kangaroos under heavy load at low speed in third, 4th, 5th and 6th

under acceleration boost climbs as normal sits at a touch above nominal max.boost for a couple seconds then bang ignition or fuel cut or whatever the cur-sed thing is doing.