need help with my audi s4 2.7 biturbo

[lotuis]

Hi i sorry for my bad english but i need help with my audi s4.

I have a audi s4 2.7 biturbo 1998 mod and i have some performance problem.
My problem is when i'm out driving all is good when you drive normal but right away when you hit the pedal to the floor and have had a few hard acceleration's the car losing some power and the noise from the exhaust get's louder.
It still pulles pretty hard but it is like 10-15% off power disappears.
And it sounds alittle like i'm losing 1 sylinder by jugdeing from the sound it is making, but there are no misfire and i have chech with a vag com and there are no misfire detected.
but if i continue my drive after maby 15min off normal driving the problem goes away but the min you do a hard acceleration again the problem come back right away.

I get no fault codes
it is chiped and have a upgraded exhaust all the way

I really hope someone can halp me with my problem

[jimmer009]

To me it sounds like your feeling timing pull. Your car does this to protect itself. Probably caused buy high iat's. Witch is caused by heat soak.

The noise really sounds like a turbo going bad. It hard to tell from your info and ppl know better than me I'm sure. But to fight iat's (intake air temperature) you need new/better intercoolers or water meth injection.

[getslideways]

If you have VAGCOM check what the EGT sensors are reporting? A bad EGT sensor can cause the car to run excessively rich and feel sluggish/low on power.

[lotuis]

Hi again i did check the resault on my egt sensors but the reading was alille wired i got this up under my test:

Egt temperature bank1: 800/min
Bank 1: 15.8%
Egt temperature bank2: 1.2%
Bank 2: -1,6%

and my air instake temp was around 30c`

does this tell you anything?

[Glennb]

could be your 02 sensors
bad o2 sensors can cause the car to go into limp mode which reduces your tubes to about half power.

[lotuis]

no i have just replased all my o2 sensors becourse i had some fault code on them
was hoping then that it was the o2 sensors that made the car behave like that but no.

[lotuis]

nobody have any idea for this problem???

[james 408]

you need logs for people to help. absent codes we'd just be wild guessing.

egt, 02 sensors, MAF sensor, or problem with boost pressure could all explain your symptoms -- even without a code. If you watch the misfire counter, you can determine if it's cylinder specific as well and start your diag.

[AvantGuard]

A faulty N75 valve will cause problems like you are experiencing. Try unplugging it and see how it runs. Just went thru this myself.

[vavJETTAw36]

Hi again i did check the resault on my egt sensors but the reading was alille wired i got this up under my test:

Egt temperature bank1: 800/min
Bank 1: 15.8%
Egt temperature bank2: 1.2%
Bank 2: -1,6%

and my air instake temp was around 30c`

does this tell you anything?

Huh those aren't even temperature. 800/min sounds like you're idle speed, 1.2% I have no clue. Bank 1 and 2, if they are correct, are way off from each other which can be the case but isn't usually. If this is accurate, I'm thinking you have ignition related issues on your passenger side causing misfires at WOT.


Sent from my iPhone using Tapatalk

[lotuis]

hi again.
My power problem is gone now i tryed like AvantGuard said and i did unplugg the n75 valve and tok a drive and it had less boost like you will expect from unplugging your n75 but it diden't lose any power under hard acceleration
and after a while i stopped the car and plugged the n75 back again and now it goes better than ever
i don't losse power anymore but the noise is still there sometimes but no power lose anyomre.
So a very big thank you to AvantGuard and all who took there time for trying to help me with my problem :)