I´m getting boost spikes

[psiconauta911]

Hi everybody,

My ABY is completly stock except for a KN panel filter.

Sometimes but not always the engine cuts when under full aceleration and after that it cuts whenever I acelerate more than half throtle. Then problem goes away for a while.

I´ve now fitted a boost gauge and discovered that it cuts when the boost spikes to 20/22 psi more than the 15/16 overboost psi.

First I thought it could be the WG diaphragm but that would cause the boost spikes to be always, I think, since it would let pressure pass all the time.

Now after serching the forum a lot I´m still not sure but I´m suspecting my N75 is the culprit,

Has anyone had the same problem? Does anyone know the solution?

This is potencially very dangerous if I´m overtaking because I never know when it´s going to happen again!

Thank you all in advance.


Pedro

[prj]

Have you screwed down your wastegate screw?
Is the N75 valve connected correctly?

[spink]

I had a similar issue recently,changed various sensors (after vagcom said they were bad) but the problem still persisted.Was getting to a point thinking it was a broken wire somewhere then thought i would swap the ecu for another one,sure enough its been fine ever since.Hoffer put a new map sensor into the bad ecu for me and now its fine

[prj]

It's always possible that there are cold joints in the ECU, but that's a lot more unlikely than the usual issues.

[EspenW]

Check the N75, good chance that it is leaking, allowing boost to spike.
Same problem on mine back in the day.

[psiconauta911]

Hi all and thank you all for the quick replies.

First as I said it´s stock so the wg is still original and not modified or "screwed".

People at Audi have swaped a lot of sensors on mine including the MAF but with no results and no costs by the way, it always registers some fault code diferent every time around.

I´m not sure if they ever changed the N75 but I´ll check with them, if not I´ll give it a check myself to see if it looks ok with no leaks.

If by the way is a ECU related problem then I´ll be in trouble because mine as an imobiliser and S2 ABY are quite rare here in Portugal it will be realy hard to get a second unit to try out, and as said before this problem comes once every 3 or 4000 miles, and it seems to go away every time I reset the ecu by disconeting the battery but I´m not really sure about this last part.

[[RPM]]

I thought aby were not sold in portugal...at least the s2 aby like mine
was your imported?

[psiconauta911]

Not imported, there are more or les 6 coupes and 4 or 5 avants.

Mine is an avant

[prj]

Please post all the codes...

[psiconauta911]

Sorry for replying just now but I have no codes, this has been going on for 5 years now but the car was asleep for the last 3 and it´s back on the road for 1 year.
First time it went to the audi garage at 90000KM and they found that the fuel filter had never been changed and it had a smal hole in the IC, after the new filter and IC it went ok (problem solved I thougt), at 110000 same symptomes new MAF and new something else I don´t recall and again new something and the problem still present, I then changed Audi dealer (very happy now) they refunded me for some of the parts and changed the fuel filter at 150000KM and it´s OK again, at 170000 changed the spark plugs and it´s OK again(the ones I had where not at their best) and now the problem again every time I have a code of MAX. BOOST EXCEEDED and some others that I already know aren´t real because I have already changed those parts.

The boost spikes happen from time to time and go away if I reset the ecu by disconneting the battery, then it´s OK for a while and some time later it happens again, since I only have the problem every other 5000KM it´s dificult to pinpoint if the last solution was indeed effective and the fact that I don´t go full throtle very often makes even harder for it to come up. One thing I´ve noticed is that it happens usualy when I full throtle in 6st with low revs (+/- 2500rpm).

[psiconauta911]

Tried a new ECU and the boost spikes are still there next is the WG menbrane or diaphragm.

[Smiley]

I would try an other N75, if available..

[psiconauta911]

First diaphragm and if doesn´t work N75 will be second.