RS2 No boost after 30seconds of startup

[GrantGam]

Grant: You should post this on the "S6 timing" thread as well. Could be the answer there too.

Yo,

Posted in the S6 timing thread. Hope it works for someone else too!

Grant

[UrS4boy]

Hi all, I know this is an old thread... but if anyone is having issues with limp mode, then there is an easy first check: remove and clean the MAF sensor. A cotton bud and contact cleaner does the trick and it worked a charm for me. Just a little dirt and grime on the sensing element was causing intermittent 'limping' which I didn't even know existed at the time. I thought I had an engine timing/misfiring problem. Luckily, it was an easy and free repair from someone who is useless with a spanner Take it easy, Grant

Grant: You should post this on the "S6 timing" thread as well. Could be the answer there too.

[GrantGam]

Hi all,

I know this is an old thread... but if anyone is having issues with limp mode, then there is an easy first check: remove and clean the MAF sensor. A cotton bud and contact cleaner does the trick and it worked a charm for me. Just a little dirt and grime on the sensing element was causing intermittent 'limping' which I didn't even know existed at the time. I thought I had an engine timing/misfiring problem. Luckily, it was an easy and free repair from someone who is useless with a spanner

Take it easy,
Grant

[UrS4boy]

Boost issue was because the hose leading to the MAP sensor was cut in 2.

Glad you finally got your issues sorted.

The loss of boost is common with the UrS4s when the boost/vacuum signal hose comes off of the moisture trap (the Oetikker (sp) OE clamps get weak and the hose comes loose with time). This is not a problem with the UrS6 and shouldn't be a problem with the RS2 because of the location of the moisture trap. However, a cut hose will definitely cause the same problem.

More MAP boost signal hose info here:

http://forums.quattroworld.com/s4s6/msgs/20401.phtml

[macspring]

RS2Zuidafrika,

Thank you for posting the final outcome of the issues affecting your RS2.

Also just glad the fighting has stopped ! ...

[prj]

Interesting that you got a signal too high and not implausible signal or signal too low in that case, which has been my experience...
Certainly a first.

[RS2ZuidAfrika]

Time for an update boys.

Boost issue was because the hose leading to the MAP sensor was cut in 2.
Warning light on dash and beeping was because of a power steering leak.
Vibration upon deceleration was a gearbox mount that allowed the box to jump up and down.
Brakes are perfect no hassles.

Doing a coolant service as well because i developed a major leak while boosting.

I want to take this opportunity to thank each one of you for contributing: even if your assumption or theory was not directly useful, i certainly learnt a lot from all of you.
Will keep you updated

[prj]

Which fault codes?
Fuel pressure and so on will not put it in limp mode.

[RS2ZuidAfrika]

small update there chaps..
Decatted the car and the cats were utterly hideously blocked and disintegrated.
Boost problem persists, but she boosts all the way up in first and second, very strong indeed.
thereafter usual issue with no boost until she restarts. We are investigating the fuel pressure and the pressure coming into the MAP.

Feedback coming soon

[rizzono1]

This is an interesting thread, one of the last times I drove my RS2 i noticed the turbo was not working and I am sure I had seen the (!) symbol flash up. Then a month later i drove and it was all fine again. Car has now been parked up since January since I have been out of the country. I thought it was down to lack of use. I am just away to get it through the MOT when i get back. I will have a better idea of things to look at if the problem comes back. I will let you know if i find anything.

Great information guys keep up the good work.

[prj]

I find it odd as well that the code occurred after the other issue.
That is why I keep telling him to get it cleared and see if it reliably comes back all the time.

Maybe it's just a fluke and the reason for the limp home mode is different (MFTS and so on).
But also maybe the MAP sensor malfunctions at higher pressures.

As for the timing coming in and out of alignment - I am pretty sure just once is enough and the ECU will go limp mode until you restart it.
I think that is what happens also if you unplug the hall sensor and then plug it back in again. But I might be wrong on this, as I don't remember 100% for certain.

[twoqu]

It would probably have the same result as incorrectly set cam timing - the hall sensor fault.
As I read it he implied that the OP moved the cam timing to get rid of the fault. In reality, the OP reset the cam timing to the correct RS2 setting from the incorrect standard setting. So the vehicle is now set correctly and the Hall sensor fault has gone. If had been an ordinary ABY/ANN it might have been a valid point.
Its not very well documented if at all other than on here!
Now we have this other Map sensor code which was not apparent before! Such is the joy of working on cars!
As PRJ has said, you cannot ignore it especially if it is responsible for the limp home. So it needs to investigated. Bit of a coincidence it occured straight after correcting the other issue.

[UrS4boy]

One question: IF the cam belt crank pulley key has sheared and the pulley is moving a bit retarded/advanced when the engine is under power/off power, how would the ECU react to the fact that the G40 shutter window on the exhaust cam sprocket is moving position randomly? (That is what Steve E. is saying, nothing about RS2 cam timing per se).

Dmitri: Thanks for your clear answer above. I wonder if RS2ZuidAfrika can find a "spare" RS2 ECU that he can borrow to confirm the MAP issue 110%.

[twoqu]

Not sure how many RS2's this bloke has worked on in N America, but as we know on the Forum (a bunch of amateurs) the cam timing on the sprocket is incorrect if you line all the marks up on the RS2. Thats why it has to be set up a tooth out to avoid the Hall sensor fault and the associated odd performance. Why Audi did made the different pulley but did not amend the marks only they know. Its a common mistake as people assume the marks should all align.
Unfortunately all the OP can do is eliminate whatever he can based on the experience of others with whatever information we can throw at the problem.

[prj]

Yes, let's ignore the obvious code, which gets only set when MAPout = 5V in the assembly code.

The reason they had to move the belt is most likely because it was timed up wrong.
The RS2 has specific timing where you can set it one tooth advanced and one tooth retarded. But perhaps you have never timed up an RS2, since they are not that common in Canada.

I have also seen one of these sensors go bad.
Fact of the matter is, as long as that code is in there and it is impossible to erase, you will not get any boost. That code means that ECU sees a constant 5 volts for a certain duration of time on AN1 of the boost chip.
There is nothing else that will trigger this exact code.

So whether it is the MAP sensor, an op-amp or something else on the MAP signal going to the processor, this has nothing to do with any timing belt.
Further more, any timing fault will not give intermittent boost. There will be just no boost all the time.