[s-cars] cut-off under WOT - Over boost cut-off

[chris chambers]

Gentz;

It sounds to me like the ECU is sensing an "over boost" situation tripping the over boost cu-off, 
which can be caused by:

1. Boost leak - do a pressure test of the pressure side of the turbo hose 
2. Bad MAF - clean or replace MAF
3. MAF has a bad connection at the MAF cable, clean the connectors on each

From http://www.sjmautotechnik.com/trouble_shooting/20vboost.html#chklist 

Begin Copy n paste -------------------------------------------------------------------------------------------------------------------------------
Overboost Cutout?

ECU fault code 2224? If you are encountering an overboost condition which is causing the ECU to cut the fuel pump, and you have stored the 2224 ECU fault code, here are some items to check out. 

You may have a leaking wastegate Diaphragm, test the wastegate diaphragm for leaks below.

You could also have a leak in the boost hoses between the turbo exit connection and the throttle body. 

If you have a hand pump or an air compressor, you can make up an adapter to fit into the hose that connects to the turbo inlet, and this will allow you to pressurize the air from the turbo inlet, through the turbo exit hose, through the intercooler, from the intercooler exit hose, and from the metal intake pipe to the throttle body and check for any leaks.. Use a pressure regulator set to about 15psi if you are using an air compressor. 

You can also do a visual check of the turbo exit hose underneath the car and look for any signs of oil leaking out of the turbo exit hose, indicating a leak. Normally a small amount of oil vapors and mist are sucked in by the turbo from the crankcase breather system, and this oil mist will typically show up outside the hoses, or intercooler connections if a pressure leak is occurring. 

Check and or replace the ribbed intercooler exit hose as well, these often split open on the bottom side, in-between the wire re-enforced rib areas, due to the crankcase breather oil mist in the system. Removing the hoses and inspecting them is also a good idea on high mileage engines. 

If you don't have any leaks in these hoses, check the vacuum/boost hose that connects from the back of the intake manifold to the ECU inside the car. 

See below for details. 

I have run across a couple of 20V Turbo cars which had a 2224 code stored inside the ECU and were getting the overboost fuel pump cutout, even though the boost was only going up to 1.0-1.2 bar. 

In the first case this would occur only when the throttle was quickly floored, and would not happen if the throttle was gradually opened all the way. In the first case, it ended up being a defective MAF sensor. In the other case it was only a poor connection at the MAF sensor. 

Try using some electronic contact cleaner on the MAF connector and terminals, and see if the overboost problem is eliminated.
End Copy n Paste ---------------------------------------------------------------------------------------------------------------------------------



HTH
Chris





----- Original Message ----
> From: AaronT <atay101 at gmail.com>
> To: Andrew B <andrew.sb at gmail.com>
> Cc: s-car-list at audifans.com
> Sent: Sun, December 27, 2009 2:50:51 AM
> Subject: Re: [s-cars] cut-off under WOT
> 
> Mine is doing the exact same thing.
> New plugs
> 1.5 yrs on 034 HO coils
> Only under max boost.  Very momentary brick wall shut down like rev
> limiter....Flicker of the CEL
> Any ideas out there?  Considering trying more coils as this was the same
> symptom the HO cold cured when I bought them...
> Thanks
> Aaron
> 
> On Fri, Dec 25, 2009 at 8:24 AM, Andrew B wrote:
> 
> > Interestingly my car developed the same problem just yesterday.  I was
> > cruising along as normal, then tried to accelerate from a light and
> > got a "brick wall"/rev-limiter effect.  I stopped, inspected, saw
> > nothing wrong, wiggled the coilpacks anyways, then shut off and
> > restarted the car, microsoft style.  Drove out of the lot, and the
> > problem was gone!?!????? (mostly ?)
> >
> > It didn't resurface for the rest of the trip, but I occasionally saw
> > the check engine light come on very briefly (<1 second) but that was
> > it.
> >
> > Fluids look good, no weird sounds or anything.  Kind of stumped.
> > Otherwise the car ran like a champ, and not having to stop and
> > reinflate my tire before every trip is nice...if only I could prevent
> > running out of washer fluid.
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