Boost stops at 1.4bar - N75?

[Vorsprung durch Technik]

Ooops It would be nice to keep it simple and just read it the way Audi intended by reading the LCD display.Use that as a datum?

[geneandbolly]

my display shows 2.2 bar maximum too . .

[geneandbolly]

Ooops It would be nice to keep it simple and just read it the way Audi intended by reading the LCD display.Use that as a datum?

that's over educated boffins for you, mark!! always showing off that they know more than you do . .

[hunker7]

my display shows 2.2 bar maximum too . .

Don't you have a picture too, or maybe a video that shows how quick your car is?

[newsh]

And do the check where you run it with the N75 disconnected so you get an idea of how much boost control the ECU is actually doing.

??
And check timing marks!

[hunker7]

??
And check timing marks!

I thought i didn't touch timing belt, but i needed an access to cam sensor, so the pulley was off, maybe it did move by a tooth. Will check tomorrow definately.

[hunker7]

And that also could be why it's vibrating at idle

[UrS4boy]

I thought i didn't touch timing belt, but i needed an access to cam sensor, so the pulley was off, maybe it did move by a tooth. Will check tomorrow definitely.

When you do the cam sensor alone, without renewing the timing belt, you *should* zip-tie the belt to the cam pulley, or mark the position of the belt on the pulley with white-out or the like, to prevent moving a tooth or too. All that said, it is probably difficult to move a tooth because the cam belt is captured strongly by the crank cog and is very unlikely to move down there, even if you tug on the belt up at the cam.

HOWEVER, you have now broached the topic and need to check the cam timing against the crank. *IF* you were out by a tooth, it would definitely explain why you can't get the proper boost (assuming everything else, e.g. N75, is fine and there are no boost leaks).

Cam timing post:

http://forums.quattroworld.com/s4s6/msgs/136943.phtml

G40 cam sensor replacement DIY by Nate P. (Imquattro):

https://plus.google.com/photos/104138090013789212848/albums/5227437779355510001?banner=pwa&gpsrc=pwrd1#photos/104138090013789212848/albums/5227437779355510001

Photo showing cam belt zip-tied to cam sprocket (note: broken magnetic bit of the G40 stuck to the inside of the cam position shutter wheel.)

[hunker7]

I did zip tie it, but i didn't have second pair of hands to help me, so it might have jumped a tooth.

And thanks for the timing info

[UrS4boy]

I did zip tie it, but i didn't have second pair of hands to help me, so it might have jumped a tooth. And thanks for the timing info

If you zip-tied it at the cam sprocket, it is very UNLIKELY to have skipped a tooth because the only other point where that could happen is at the crank cog and that is almost impossible. Nevertheless, you do need check the crank to cam timing as per that post.

[hunker7]

Just checked the timing, and it's out by a tooth.

When I was removing cam pulley, I zip-tied it...it might have jumped a tooth, or when timing belt was changed not so long before I bought it.

I will be taking the timing belt off next Sunday, I want to change water pump too, as there is no record of it being done when timing belt was done.

[K Simmonds]

That's a pain but at least you've found your problem by the looks of things.

[Majorcina]

Hope it fix all the problems máte

[UrS4boy]

Just checked the timing, and it's out by a tooth. When I was removing cam pulley, I zip-tied it...it might have jumped a tooth, or when timing belt was changed not so long before I bought it. I will be taking the timing belt off next Sunday, I want to change water pump too, as there is no record of it being done when timing belt was done.

My guess is that it was like that when you bought the car. Regardless, IF you absolutely wanted to do the water pump, then you will be into the full monty. You might want to read this: http://12v.org/urs/FredMsTimingBeltR&RDIY.pdf

HOWEVER, if you just wanted to see if this is your issue first, and assuming that the timing belt is tensioned correctly, I would try to "adjust" the timing at the cam end, and not open up the whole timing belt/water pump can of worms just now.

To do this, I would mark the current position of the belt where it should be, i.e. at the notch on cam cover, with white out and then start into the G40 cam sensor procedure. However, when you get to the point where you would zip-tie the belt to the cam sprocket, you don't. You slip the cam sprocket off the cam, keeping the belt under a bit of tension (you might need an assistant for this). Then slip the belt off the sprocket (keeping a bit of tension on the belt. While your assistant holds the belt, return the cam sprocket to the cam shaft and with the bolt back on, rotate the cam the one required tooth (luckily is needs to rotate clockwise). With the cam now in the correct position, remove the sprocket and slip the belt back on with the mark on the belt you made. Now the mark should line up properly and the mark on the belt (which never actually moved) should line up with the mark on the cam sprocket. Finish off with the proper tightening of the cam sprocket bolt (holding the cam sprocket without damaging the G40 shutter wheel on the back of the sprocket).

All of this assumes that your timing belt is tensioned properly to begin with. If it is too loose, then you are probably into the Timing Belt procedure and you might as well do the water pump.

[newsh]

I thought it had to be the cam timing, it was really the only thing left to check that would reduce boost but not all the way to limp mode.
Dude your car is going to Fly!