Limp mode under load

[K04-B6]

Hey guys,
I keep hitting limp mode when I'm under load. When I'm in 3rd, 4th and 5th gear around 2000 rpm, if I floor it I keep hearing this weird hissing noise and my Dv just "bouces" and car falls into limp mode. Would anyone know what would cause this? I've been dealing with this all winter and it's getting pretty annoying! I have no boost gauge either...

Thanks

[K04-B6]

The car holds boost throughout higher rpm's. I'm wondering if it could be a small leak?

[xhackerekx]

oem or aftermarket DV ?

[old guy]

He's running a Forge 008 DV so I don't think the DV itself is the issue. However, it could be a problem with the boost/vacuum signal going to the DV.

Have you closely checked the line from the intake manifold to the N249 and from the N249 to the DV? Have you bypassed the N249?

Have you determined that you are actually going into limp mode by a reduced signal to the N75 or is it just based upon the lack of boost?

You mentioned that your boost returned to normal at higher PRM's. What is normal for your current K04 setup? (Oops! Never mind. You mentioned that you didn't have a boost gauge).

Another possibility is that the ECM is activating the N249 and applying a vacuum signal to force open the DV. I had that happen several times when I was running the GIAC big injector file. It will occur when you go into boost faster than the ECM expects and the ECM has already maxed out the CF's. To protect the engine it forces open the DV. That would explain the audible release of boost pressure at lower RPM's but still maintaining boost at the top.

[K04-B6]

My N249is is by passed so maybe that's the issue... I ran with it by passed for a good 4 months with no issue. I've also check the line going from the intake to the Dv and it held pressure before I put it in place. I feel like it's lack of boost. You hear it building up boost and it just makes a really loud noise almost like the diverter is just letting air escape and then bouces and I fall into either soft limp mode or limp mode. No cel either, yeah I know I'm not helping my case with having no boost gauge but at the moment I can't afford one. On my setup I'm currently running the second mode on 91 octane, I have 4 modes I can choose from but Apr could never help me out on what psi I'm running for each modes... By the sounds of it maybe I should just run my N249is and see if that's the issue. Thanks for the input. I should do a boost leak test also. Could a vacuum leak cause this as well?

[old guy]

If you have bypassed the N249 and you are still hearing a pressure loss your problem is elsewhere. If the N249 is bypassed the ECM can no longer exert any control over the DV to dump boost. You should perform a boost pressure test to see if you can find where the boost loss is occurring.

Good luck! (and pick up a boost gauge;-)

[K04-B6]

I'll run a test this week and post feed back. Thanks for the help! Boost gauge is my next purchase after I move.

[K04-B6]

Sorry for the long wait, I got caught in other things. I did a boost leak test tonight from the TIP "plugged the prv valve at the TIP" and I did not hear any leaks... So now I'm stumped on what it could be. if i'm in third, fourth and fifth gear at 2,000 rpm, I floor it and the car has a hard time building boost, I then get a huge woooossshhhh sound and then falls into soft limp mode. Third gear will sometimes make it, it'll hold and produce more boost but it has a hard time.. sorry guys I still have no boost gauge, at the moment its not in my budget as I'm moving in the next couple weeks.

*EDIT* I also forgot to mention that when i'm around 3,000 rpm and I floor it, if boost does build up, the car struggles the whole way up and the boost keeps fluctuating up and down ti'll redline.

*EDIT* Another thing I forgot . When I was doing the leak test I could hear my oil bubble below... is this normal?

Thanks for any input

[K04-B6]

Anybody?

I'll try to stick my go pro in the engine bay tonight and get a video of the sound, it's dreadful to hear this noise and I'm worried that possibly there's to much pressure in the crankcase but I don't how to diagnose this. If I unplug my N75 valve at the connector will it react in the same way as if I were to just pull off the top vacuum connection?

[K04-B6]

Alright so I took a video on my lunch as well as checked on my ebay vag com what hidden codes I would find after hitting limp mode.

Here are the photos I got

[IMG][/IMG]



From what I am gathering I would assume I am overboosting... I don't understand how under load this would happen but at hight rpm this problem doesn't occur. Any input on what to do next would be appreciated.


If you guys want me to post the video I can still try but with the codes it should be clear what is happening.

Thanks guys

[K04-B6]

You will hear in the video at around 50 seconds to a minute I'm in 4th gear at 2,000 rpm. You will hear a high pitch noise right before you hear the air bounce which causes me to fall into limp mode. I ran a boost leak test last night and I have no air leaks in my system. I wonder if my wastegate actuator is leaking since I don't think that part is tested when doing a boost leak test at the tip but I'm not certain about that.

[old guy]

It sounds like you may have a problem with your N75 boost control valve. Try logging the N75 along with the requested and actual boost. If you see the Boost increasing while the N75 duty cycle drops off that would be an indication of a problem with the N75 sticking.