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S3 (8L) BAM Over-boost problems


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#1 Redline2008

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Posted 09 September 2008 - 07:52 PM

Hi guys, looking for some help before I lose my mind over my 2002 BAM S3.

Soon after I got the car, I noticed it wasn't boosting correctly and kept going into limp mode. Returned it to the independent dealer I bought it from and their workshop. They confirmed it was showing the 17963 - Charge Pressure: Maximum Limit Exceeded error on the VAG-com

They replaced the MAF, the N75, the DV, some of the boost pipes and the turbo with a refurbished unit.

This didn't solve the problem, so they then passed it onto Tyneside Audi who have also replaced the MAP sensor, still with no solution.

So I'd really be interested if anyone has any views on what else it could be before I decide to pursue a refund.

Cheers.

#2 PetrolDave

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Posted 14 September 2008 - 04:46 PM

They confirmed it was showing the 17963 - Charge Pressure: Maximum Limit Exceeded error on the VAG-com

Has the car been chipped?

#3 Paul

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Posted 14 September 2008 - 10:17 PM

It could well be chipped. remapped with a agressive map.

The N75 thats been replaced, controls the turbo's wastegate, which inturn has already been replaced with a recon turbo.

Another valve is the N249, which controls the opening/closing of the Diverter Valve, and hence excess boost.

http://www.tyresmoke...n249-valve.html

#4 Redline2008

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Posted 15 September 2008 - 04:37 PM

Thanks for your replies.

Both places claim to have checked that it hasn't been remapped, how much I believe them on that I'm unsure.

If the N249 was faulty, would it show any specific fault codes on the VAG-Com? As far as I'm aware it's only been brining up the 17963 code.

#5 BW2309

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Posted 28 September 2008 - 03:02 PM

The N249 valve can fail or be sluggish without recording a mechanical fault but this is not too likely as the N75 is the primary control for over boost control. The N249's main uses are to regulate part throttle boost and to recirculate boost on gear change/throttle release.
It's a good idea to check boost pressure specified and Actual values with VAG COM. The measured value block for this is 115. You will see if then the boost is genuinely reaching high levels or if another issue is making the car "request" less boost. If standard you should be reading up to about 2000mBar - That's 1Bar boost plus atmospheric pressure.
Things to check include altitude correction factor - if this fails the car thinks the air is more or less dense than it really is and so this affects what boost is safely allowed.
Also this check with VAG COM will indicate whether the boost pressure guage is operating correctly.
Check that the vacuum tank (ontop of the cam cover, above the coil packs) has not got a cracked outlet or pipework. This can affect the ReCirc vale's operation too!
Good luck!

#6 Tame Technician

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Posted 20 October 2008 - 06:23 PM

Sounds like the Boost pressure sensor to me, car thinks its over boosting when perhaps its not?

As suggested above you need to monitor the boost pressure sensor while driving with the VAG COM? or have you local audi centre do it with there 5052. If you have a mechanical boost pressure gauge to compare against even better.




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