N249 Fault?

Tastyterrier

Tastyterrier

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I've had an intermittent acceleration hesitation fault recently and I hope maybe one of you guys can shed some light on it.

It occurs when I've been sat in gear for a while or sometimes when I change down. The best way to describe it is as if the turbo has shut down, I'm still accelerating but with no boost. If I come off the accelerator, wait a few seconds then try again, the power is back. Also if I change up the power comes back, but not if I change down.

I've gone through the obvious: New coilpacks all round, new after market DV ( I now have a fully function Turbosmart DV going spare!), MAF sensor (disengaged and the fault still occurs), TB clean and alignment and accelerator pedal sensor reset. There's also no leaks as far as I can see.

The last port of call has to be the N249 valve, I guess there's a possibility that as I'm remapped with an N75J, there could be a boost spike issue that the N249 is trying to solve, but it doesn't explain why it's intermittent and the car isn't going into limp mode. Do these valves have a habit of going wrong? Is it just a case of cleaning them? I know you can do a bypass of this valve, but as it's effectively stopping the car from over boosting, it's a safety feature I want to maintain. Especially as it's remapped with the N75J.

When the fault doesn't occur, the car pulls hard and smooth through the rev range. It idles well and is drinking a normal amount of fuel.

I don't have access to VAG-com right now as the laptop has packed up, so I hope one of you guys can suggest something solve it from this description :icon_thumright:
 
I wouldn't expect the N249 to be causing the issue and for testing purposes you'll probably be fine just to bypass it for a few hours to see if the problem goes. Have you tried going back to the standard N75 valve?
 
my car used to drive simmilar to yours when i was running my n75j with the n249 valve, i think the n75j effects the n249 valves so if you dont want to bypass the n249 then i think your going to have to go back to standard n75 and change the n249 aswell, or you can bypass the valve and then it should be ok, as said above you can always bypass just to make sure it is the n249 at fault.
 
Apparently one of the risks with using the N75j valve is that your car may hit limp mode, it's a lottery...
 
Sorry to jump in here but i'm having a similar problem. How do you bypass the N249 just to test?
 
audi upgrades
Cheers for all the replies. Have any of you guys done the bypass, any potential problems I should be aware of?
 
i have done a bypass only thing i recomend is to fit a boost gauge so you can keep an eye on the boost as the n249 is there to stop over boost which is unlikely to happen anyway. plus the car runs much smother with it bypassed especially with the n75j fitted.
i would take some pictures of mine but my brother has my camara on holiday.
but basically all you need is a T piece, some vaccum hose, a 13mm bolt and a jubilee clip.
the pipe that comes out the n249 to the dump valve need to be choped and blocked off using the bolt and jubilee clip, then run a new vaccum line from the top of the dump valve to a inlet vacum line i used the fuel pressure regulator vaccum line this is where you need the T piece, leave the n249 plugged in to stop eml comming on and all other pipes on to the n249 also job done,
you can remove the whole lot but its more complicated then this way but would do the same thing anyway
 
audi upgrades
Thanks for the great link Westle. My engine bay doesn't look like this though, here's a pic:

DSCF3402.jpg


I'm guessing the N249 valve is housed under the bracket mounted to the manifold, this appears to be where the hoses from the vac reservoir and DV go to:

DSCF3403.jpg


To repeat S3 Kev's excellent advice, I basically cut the one that originates from the DV and plug it on the N249 side, I then put a tee in on the hose to the fuel pressure regulator:

DSCF3404.jpg


...add in a tee and link it to the DV? Wouldn't this cause problems for the fuel pressure regulator?
 
your n249 valve is probably not the same as on those pics, its on top the rocker cover under the plastic engine cover
 
The only things on top of the rocker cover are the coilpacks and vacuum reservoir, no sensors. The only electrical harnesses going into this area are for the coilpacks.
 
oh ok so maybe yours is more like the pics above, well if you follow the vaccum line from the reserviour then that should go to the n249 valve as the reserviour is used by the n249 as a stored vaccum centre
 
The bypass is fitted. So far so good, the car seems to be accelerating smoothly. There's no major change in throttle response, but there's no loose of boost either.

As the N249 is a safety valve for over-boost situations, I've replaced my N75J with the standard fitted N75. Can I run the N75J safely? Is anyone doing this on a k03s turbo? Know the easiest way to know for sure is to fit a boost gauge, but I'm not keen on having one fitted on the dash. Is there another method of checking for over-boost?
 
Have you bypassed the N249, have you tried just replacing the N75 back to standard and leaving the N249 be...
 
If your car is running better I'd leave the standard N75 on and get a new N249 fitted, not worth the risk killing your turbo...
 
Anyone know how much youre looking at to have a new N249 fitted?
 
Finally managed to get round to doing this. I've noticed that the DV (007p) seems to be alot quieter than before. I've tried fitting it the other way around but still not as loud as it has been. Any ideas why?
 
Suppose that's a better way to describe it.

Car certainly drives better with the bypass but unfortunately didn't solve the surging problem when coming off boost.

Unsure what to try next :uhm:
 
Seems to jerk when I come off boost but only on part throttle. If I've got my foot planted it doesn't do it. It happens between 2.5k and 3k rpm mostly in 1st and 2nd gear.

Problem started after the remap. So far i've changed the MAF, the N75 to the J valve, tried another 710N which didn't resolve anything so fitted a 007p DV (experimented with both green and yellow springs) all to no avail :(

I've had it scanned with VAGCOM several times aswell.... nothing showing up.
 
Mine is doing exactly the same although when it does it the traction control light comes on and stays on, even when pressing the t/c button on the dash. Also on most occasions, the abs light comes on. Strange as when it is ok, it is going well.
 
Did you find out why it was jerky when partial throttle? My car can sometimes feel as if you just touched the brakes when not on full boost its quite jerky when this happens, does anyone have any ideas what it coluld be?:shrug:
 
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