Check Engine Light Code P0299/Underboosting Issue

[shadowxalex]

Hi everyone. I currently drive a 2007 Audi A4 Carbiolet. It has about 98k on it and it has been amazing up until last summer. I don't know what caused it but my check engine light started to come up and I could feel that I wasn't getting the right amount of boost, it felt really slow. I took it in to my local BP repair shop to have it checked out. I know it's not the Audi repair center but my family has been using these guys for almost 10 years and they are very good and almost always use OEM products. Anyway, they checked it out and said the code normally relates to the blow off valve and I confirmed it when I looked online to see what other people were saying. They put in a new valve and sent me on my way. This was around 80k but the issue wasn't solved. The code kept coming and my boost was still not great. I bought an OBDII reader and have been using Torque on my phone to check the boost levels and I was right, I was getting between 5-7 PSI. Then everything went to tell. Every time I accelerated hard I would get misfires and my car would sputter. Ended up being that the turbo went bad.

Audi quoted me about 2 grand to fix it but one of my best friends is a mechanic and offered to put it in for me. I bought a refurbished OEM turbo (exact one) and we spent the entire weekend putting it in. After that everything was perfect, no more issues, and my boost went back to around 14 PSI. This was back in November when we installed the turbo. Fast forward to April and the car started doing the same thing. Started with the check engine light coming up with the same code and my turbo started underboosting again. The underboost doesn't happen all the time however. In the mornings the boost works fine and I will get 14 PSI and randomly it will start boosting at 5-7 PSI. When I mean randomly I honestly mean randomly. It didn't matter how hard or soft I was pushing the car. Sometimes it boosts fine and I drive around normally and I get to a stop light and when I go it starts underboosting. Check engine light is also random and sometimes will come on when I accelerate hard or when I just drive normally. I went back to BP and they checked the blow off valve again and they said it had no problems.

Does anyone know what could be causing this issue?

TL;DR

Code P0299 and unerboost. New BV, problem got workse. New turbo in, half a year later same issue starting again.

EDIT: Diverter Valve not Blow Off Valve

[Sanjman]

check for leaky hoses like intercoolers and valve cover. It seems like after the car warms up something starts to leak. A smoke will be very helpful to find all leaks. A common problem right now are the valve covers / valve cover gaskets.

Also double check yoru diverter valve, wastegate actuator and of course the turbo. What do you mean refurbished? Did you buy it off ebay or a reputable remanufacturer?

also, if you have your old turbo, i'll buy it from you :)

[shadowxalex]

Awesome, I'll ask my friend to help me out with it. Unfortunately I'm not as good with cars as he is.

I bought directly from here: http://www.hansautoparts.com/multipl...builtTurbo.htm

Yeah, I don't think its good anymore but if you want it than it's yours. I just ask that you pay for shipping and I won't charge you anything else. Just PM your details and I have ship it this weekend.

[mtroxel]

I'm APR stage 1 so my ECU is looking for up to 17 PSI at times. That means all my boost hoses have to very tight. I've found that if the hose clamps are as tight as I can get them with a screw driver, I can still leak. Now I use a 7mm socket on a 1/4 ratchet and get them much tighter. There are 4 hoses with clamps on each end. 1) Turbo>passenger intercooler, 2) pass intercooler>boost passage under the radiator, 3) boost passage>drivers side intercooler, and 4)driver's intercooler to throttle body.

Another simple thing, is your air filter clean? How bout the snow screen where the air chamber meets the air box?

[esandes]

i had the same code once and it was due to a dirty air filter. cleaned the filter and code never came back.