wmerchle

So ever since I upgraded in spring to a K04 turbo in the spring I have been getting the P0299 code at wide open throttle. For those of you who do not know this is an underboost code. The car runs fine though and doesn't seem to go into limp mode. I am mystified.

I have checked every clamp at least 5 times, tried different diverter valves. I have logged data via VCDS on to look at specified versus actual boost and it is clearly under boosting at high RPM. Here is a link to a google drive folder with several spreadsheets on several occasions measuring block 115. Also one of the spreadsheets has N75 duty cycle.

Google Drive Folder

I also have a weird noise that occurs around 3000 RPM. I recorded it at also put the recording in the google drive folder. It is very noticeable at seconds 7 and 11 of the recording. I am not sure if the noise and the underboost issue are related. I am wondering if it is the wastegate rattling or what?

Any ideas or diagnostic tests you guys would suggest would be appreciated.

wmerchle

I updated the Google Drive link because I don't think it was working and I also have a question:

Should a APR K04 kit be requesting 33 PSI of boost? That seems really high to me? My car never reaches that which is why the p0299 code is being thrown. My car does however make about 27 PSI. Again any ideas would be appreciated.

Crash Craddock

I had the same code, ended up being a bad cat, loose on the inside, rattled at shutdown as well

ECS Tuning-Audi

Also check your suction pump (looks like the picture below) as they tend to blow apart and will throw a underboost code.





Jason

Killerk

From what I know 33psi is way to high for a K04 I haven't heard of someone trying to get a K04 to run that high of boost. 33psi is big turbo and even then it's high. I'm no expert but have done a lot of research because I was going to run one.

wmerchle

So after throwing money at my problem in the form of new parts and still not curing the cause of the p0299 code I decided to do a boost leak test. I probably should have done this first.

After pressurizing the system I heard and felt a distinct leak in the brake booster vacuum pump housing. I ordered a new pump on ECS and hopefully will have the part in the car later this week. I really hope this solves my P0299 code. I will repost after install the part and run the car hard. If I can offer any advice with this code, I would say do the boost leak test!

wmerchle

False Alarm! So after doing a little reading and research I forgot to subtract out atmospheric pressure... ~14 psi! That brings the PSI down to a much more reasonable 19 psi!

wmerchle

So I feel pretty stupid. I got the part, put the new brake booster vacuum pump (BBVP) only to find out that there is small that is an air outlet to the atmosphere. In other words it was supposed to do that. After more searching I found this post in the forums (post #18).

Brake booster suction pump?

Bottom line is that you need to block the hose on BBVP off if you are going to do a boost leak test. After blocking this off and redoing the boost leak test I could hear no boost leaks anywhere. Disappointing! I was hoping for something simple to fix to solve the p0299 code.

Here is where I need some advice. I guess I have it narrowed down to either a clogged up catalytic converter that is creating too much back pressure, a trashed K04 or a crap wastegate. I am planning on putting a test pipe on to see if that fixes things considering its probably my cheapest option. I am also going to pressure test the wastegate actuator itself. Any ideas would be appreciated.