2001 AMK S3 17963 - Boost Pressure Control: Upper Limit Exceeded

[russwuss]

Hi All,

Brand new to the Audi-Sport forum, first off thanks for saving me a little bit of money on my car insurance

Purchased a 2001 Audi S3 AMK at the weekend.. very happy with it apart from one issue it's developed.

When I put my foot down in 3rd the boost comes on as normal, then when it hits about 4k rev's the turbo shuts off and sort of goes into 'limp' mode.

I borrowed a mates VAGCOM from work and did a fault scan, only fault it found was 17963 - Boost Pressure Control: Upper Limit Exceeded.

I cleared the fault and went out in the car again, put my foot down in 3rd and the issue happened again - back to the VAGCOM and the fault was back again.

Cleared the fault again tonight and logged block 115 after reasearching on here and other forums - log proved that the car achieved 2490mbar boost when requesting <2000 then went into limp mode.
I've uploaded the log here if anyone would like to take a look https://docs.google.com/file/d/0B9EEpgd7a-FXN2JHTi14VUZUZ2s/edit?usp=sharing

After researching already everyone seems to suggest the N75 or N249 valves, anyone with experience of this issue say this cured their issue? If so I'll check all piping on Saturday then go out and buy a new N75 - is there a specific part no. you'd recommend?

Other than this VERY impressed with the S3 so far, after coming from a MK2 Golf GTI (and shamefully a Peugoet 206) this is a brilliant car..

Going to try and give the car a full detail at the weekend also, will post up some pics afterwards

Thanks in advance!

Adam

 

[russwuss]

Forgot to mention, brought the car as 100% standard - so remap shouldn't be an issue.

 

[Ronin225]

I have a LCR so essentially the same engine, mine was running full stage 2 mods but still OE map
At roughly 6k it used to flow over 200g/s and boost would creep up causing this fault and limp mode (someone did explain in depth why this happens)
However being so low in the rev range i'd say it is more likely N75 related

 

[russwuss]

I have a LCR so essentially the same engine, mine was running full stage 2 mods but still OE map
At roughly 6k it used to flow over 200g/s and boost would creep up causing this fault and limp mode (someone did explain in depth why this happens)
However being so low in the rev range i'd say it is more likely N75 related

thanks for the reply! For the millions of topics I've read I'm lead to believe it is the N75.. most threads recommend the N75F VW N75 valve, standard version 058 906 283F Genuine | eBay so I'm check for vac leaks, if I don't find anything I'll replace the N75 and report back!

Thanks!

 

[Alex C]

maybe check the hose from the N75 valve to the actuator?

 

[<tuffty/>]

Try connecting the hose coming from the charge pipe that goes to the bottom of the N75 to the pipe going to the actuator... (use a bit of pipe to join the exposed N75 ports so you are not drawing in unmetered air) this should give actuator pressure everytime as you have effectively bypassed the N75... if your boost remains consistent then sounds like the N75 is iffy...

Looking at your log it only does it the once... but I assume as its in limp mode it doesn't clear until you cycle the ignition? does it do it everytime you clear out of limp?

<tuffty/>

 

[russwuss]

Try connecting the hose coming from the charge pipe that goes to the bottom of the N75 to the pipe going to the actuator... (use a bit of pipe to join the exposed N75 ports so you are not drawing in unmetered air) this should give actuator pressure everytime as you have effectively bypassed the N75... if your boost remains consistent then sounds like the N75 is iffy...

Looking at your log it only does it the once... but I assume as its in limp mode it doesn't clear until you cycle the ignition? does it do it everytime you clear out of limp?

<tuffty/>

Thanks for the reply mate, I'll give that a go tomorrow morning.. hopefully the new N75 will be here tomorrow dinner if it does prove that the N75 is iffy. So buy connecting the two pipes together there's nothing regulating the boost level, therefore I'd expect the requested boost and actual boost pressure to be close right?

Did another log today also logging block 119 as I read somewhere that's the load on the N75 valve?
https://docs.google.com/file/d/0B9EEpgd7a-FXbXZ6RTd6M3lYNEU/edit?usp=sharing
at 61secs pressure hit >2400mbar and I felt the car 'pull back' and after that the turbo wouldn't boost as high, pulled up and again the overboosting code was logged on VAGCOM.

Yep switch the car on and off and the car will boost correctly again.

Oh forgot to add, had a quick check on the piping around the N75.. all looks ok to me, revved the engine a little to see if I I could hear any boost leaks.

Thanks again!

 

[Ronin225]

Interestingly my leon wouldnt clear limp mode on ignition cycle, it had to be done via vagcom

 

[russwuss]

Hmmm, not sure why that is Ronin225 - I definitely had boost have I turned the car off and on again - however it wouldn't be instantly switch back on/off.. over space of a few hours.

Thought I'd update the post for anyone else who is having the overboost issue, my new N75 arrived today (part 06A 906 283 E) from germanautoparts- fitted within 15 minutes, clear any existing faults on the engine and took it out for a spin.

Very noticeable difference, power is now all the way through the rev range not just dumped at 3500 - 4000 revs.. peak pressure achieved was 1980mbar which is much lower than before - no faults logged when I got back after test driving - very happy!

There's a log here https://docs.google.com/file/d/0B9EEpgd7a-FXcUVNdU5wUzl3TTQ/edit?usp=sharing of the run I did after the N75 was fitted in case anyone would like to read when they experience the issue.

Now to try and talk myself out of a remap ;-)

thanks for all the suggestions!