Car is flashed with exhaust. Happened twice now, events being separated by a whole month. Was driving fast on the autobahn and car felt a bit sluggish. Switched to boost mode on the dash and under the full throttle boost was down to 0.5 bar from 1.3 bar peak. No messages or codes on the dash. I switched ignition off and on whilst driving and car went back to normal boost. Boosting normally now and all is fine. I hate intermittent problems! :-(. Any ideas?

 

Sounds like the ECU but I would believe codes would show.

 

check the codes... probably an overboost error, Im guessing in tune, or possibly dvs acting up... you need to also do a real good pressure test from the lower boost hoses... to 22 psi and it must hold for 30 seconds... between those 2 you will find the issue..
markski

 

Yep..over boost...and Mark is right...waste gates over compensating...find your leak(s)...

 

My car had similar symptoms and was throwing a soft code. Do you have a Durametric? That would be a great start. Mine ended up being a bad DME. Here is a link to the thread:
https://www.6speedonline.com/forums/...limp-mode.html

I have a feeling that my situation was unique, but you never know.

 

Thanks mate.

Car wasn't doing it for 5 years so I can rule out the tune?

Dvs how do I check those or just replace?

Hoses? Wouldn't leak be a nonstop issue?

 

It could be a "tight" leak...clamp loose enough to only leak under boost. As far as DV's...take them off and blow into them...should only be able to blow one way...

 

in addition to these suggestions you can also have a faulty check valve which will also cause over/underboosting issues. the leak will be found during the pressure test, and replacing that check valve on top of the intake ( and might as well the n75 same time ) if it's faulty will be the cause of your leak. they are just plastic valves and prone to cracking.

i just recently went thru this and prior to locating the leak i kept trying to adjust my wg's with varying degree of success/failure in that i would either under.. or over boost and discovered the bad check valve as the leak whistled dusting the pressure test. it's usually something small like a loose ic hose or a "valve". these cars can be quite the education lol

 

I think I can here the whistle during my acceleration. Where is the check valve? Easy to get to? I presume replace job. If you changed yours, part number? Many Thanks.

 

i don't think you'd hear the faulty check valve during accel. it would only be while pressure testing you'd hear it. if you hear something unusual while driving, i'd think that to be a much larger leak or possibly a bad diverter valve. or maybe an ic hose has come loose.

i only mention the check valves as they were the last thing i checked, and i'm probably not in the minority on that one.. and yet, it is a common failure leading to the symptoms you have and that i just solved. with help, i must add!

it's on top of the y-pipe, and the n75 is near there also but lower iirc. that part is a serious boost control recirc valve and it's really cheap ( bosch )_ make sure you confirm it is working 100%. the n75 and the upper check valve were maybe 60 bucks all in.