Boost of 1 bar

[nesshead6]

What have you done to your wastegate?
Own up.
It should be 0.4 bar, and that is the likely cause for your problem.

You have a combination of two things:
1) Boost leak
2) Wastegate that has an overtightened or too stiff spring, whereas homefries are meant for the stock spring.

Ok, I see where you're coming from, because of the overboost fault I should only be getting 'spring boost' after the ecu generates this error. I've never touched the wastegate (honest ) in my ownership of the car. So the next questions...

How do I check if the WG spring is too tight i.e. how tight is it meant to be?
Is there a way of checking the signal from the MAF?

Thanks.

[mouse]

Towards the bottom of this --> http://www.s2central.net/ds_G70.html page is a description of how to check MAF values with a multimeter.

I had a dying MAF which read too low on test number 4. on idle and blipping the throttle but this test just confirmed the MAF error code I had already read with Vagcom. And had totally different symptoms too - rough idle and engine dying at idle and not wanting to start at all intermitently.

( I only did the Testing the MAF – Part 1, External Checks)

[prj]

How do I check if the WG spring is too tight i.e. how tight is it meant to be?

Is the wastegate cap drilled? Is the nut screwed down?
Turn it all the way up, disconnect the N75 valve, then do some WOT runs and adjust it so, that boost goes to 0.4 bar.
If the wastegate cap is not drilled, you will have to undo all the little bolts - carefully, they are fragile and check what the spring looks like. The stock spring can be compressed using two fingers without much effort.
It sounds to me like you have a 1.9 bar spring - either way, homefries are not meant for that, so it can overtboost.

Is there a way of checking the signal from the MAF?

As the first thing, get some contact cleaner, undo the MAF connector and spray the it very generously on the contacts of the connector and also onto the MAF pins.

[nesshead6]

Ok, thanks for your advice. I am 99% certain that the wastegate has never been tampered with, but we will see... Hopefully will get some time to look at it next week.

[nesshead6]

Update - took the car out for a drive last night with N75 unplugged... the wastegate is functioning as it should, allowing boost up to a maximum of 0.4 bar.

Frustratingly enough, when I plugged it back in and drove about for a couple of hours, the car drove well and the intermittent fault didn't occur. I guess I can investigate the MAF next. It's just so frustrating that the car can be brilliant for a few hours/days/weeks then go bad again...

[prj]

Clean the connector and try fitting another MAF. Maybe you know someone with a similar car in the area.
3B, AAN, RS2 - all these are fine.

[nesshead6]

Will do. My friend has a spare MAF for his RS2 will try that.

[newsh]

@ nesshead6 Read this. http://www.s2forum.com/forum/showthread.php?t=24544

[nesshead6]

Thanks for that. So are you saying that if the fault happens, I could try to test for a bad MAF connection by leaving the engine running, reseating the MAF connector and then see what happens when I try to drive again? I thought that you had to switch the car off to stop the ecu from kicking in the overboost protection (limp home mode?). I will definitely give this a go next time it happens though.

Thanks.

[prj]

You need to cycle the ECU if you want it to drive on full boost after it hits load limiter...
In normal driving it should never hit the load limiter - load limiter usually shows that either the ECU software is run outside it's operating conditions, there is something wrong with the MAF and it reads higher than it should or there is a heavy boost leak, so more air passes through the MAF than actually makes it to the engine.

The only other thing I have seen causing this was a faulty ECU that was "repaired" by some cowboy.
I doubt it's the case here though.

[newsh]

No, switch off the engine, pull the maf connector off and on a few times and start the engine again and take it for a run, see if it makes a difference, for me this would last a few days before going wrong again. One step further is the clean the connector with a good contact cleaner like Caig De-Oxit and the final solution for me was to take the pins out of the conector and clean them properly with some very worn out 2000 grade wet and dry. You insert the paper carefully between the 2 ends of the female pin and slide it back and forth a couple of times. The pin is spring loaded so it grips the paper quite well.

This problem drove me crazy for a few years, I even bought another ECU.

Anyway its all described in that thread..