P0299 - Turbo underboost - APR Stg2 - Please help

[JaxACR]

Cliff's Notes Version
My car is throwing a code for turbo underboost. I am getting 19 psi on APR Stage 2. It's not the DV or PCV. Read on for more details.

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Hello all, I've got this nagging P0299 code (turbo underboost) that I can not get rid of, and I'm hoping someone can help. Please bear with me, this post is going to be long but I'm trying to provide as much detail as possible.

First off, the car is a 2007 A3 with DSG and APR Stage 2 (v1.1). Relevant mods are 3" catless downpipe (into stock catback), and HKS SSQV (w/ ATP DV blcok-off plate). Intake is stock.

Ok, so currently the car has 19,5xx miles on it. Downpipe was installed at around 15k. SSQV was installed shortly after that along with ATP DV block-off. I swapped in the GTI throttle pipe and the SSQV is installed on the noise pipe bung w/ a silicone coupler. On stock programming, this has been running great. Spiking about 15 psi, holding 10-11 psi. No codes ever except the P0420 for no cat.

At 18,7xx miles I got APR Stage 2 loaded (May 3). My APR dealer is about 140 miles from my house, so I did this during a planned trip. When I first got the programming loaded, I had no CEL and has holding about 17-18 psi. Drove another 250 miles that day, 95% on the interstate. Noticed I had a CEL when I got home - P0299. Changed spark plugs the next day (NGK BKR7EIX). Figured I blew my PCV.

My PCV is stock from the day I bought the car, and it is a 'G' revision. I pulled it off about a week before I got chipped to check if it was good, it was, never replaced it. After I got chipped and threw the P0299 code, I assumed it was the PCV, so I ordered a Eurojet fix. Waited a couple weeks, never had any other symptoms of a blown PCV (no whistling; not a drop of oil around the cap, on the engine cover, under the engine cover, nowhere).

Received my Eurojet fix on Saturday (May 17) and installed it. Followed the directions, arrow pointing towards the intake manifold / front of the car. Went for a test drive and the car felt a little better, seemed a bit 'peppier' on the throttle at low RPMs. Still maxing out at 18 psi, threw the P0299 code again within 20 miles.

Now I started brainstorming on where else I could be losing boost. I decided to go back and check all of the fittings on the pressurized pipes (between the turbo and intake manifold) that I had altered. Turns out, when I installed the GTI throttle pipe and SSQV, I used a flathead screwdriver (out of laziness) to tighten all of the hose clamps. Got a socket wrench and tightened up the clamps on the intercooler to throttle pipe, throttle pipe to throttle body, and both clamps from the noise pipe bung to the SSQV. All of them tightened quite a bit. I tightened all of them as mush as I felt comfortable, without breaking the plastic throttle pipe.

Confident that this must have been the problem, I went for a drive. Now it was holding 19 psi and I drove for a day with no CEL and was happy. Then on Monday I was putting a 350z in his place and the damn CEL came back on (P0299). So that night I popped the hood to check everything out. Tightened the Eurojet fix quite a bit, and I also noticed that I had stripped two of the screws on the PCV itself (freakin plastic valve cover ). I also wanted to check out the stock DV location, but was lacking tools. Went and bought a socket and some slightly larger diameter screws for the PCV. Came home and went to sleep.

Last night I replaced the two screws that were stripped on the PCV, noticed one more was questionable and replaced it, and then said "what the hell" and replaced the last PCV screw. I know that it shouldn't be affecting my problem (non-pressure side), but I wanted to make sure it was tight anyways. Then I pulled the DV block-off piece and the top half of the OEM DV that holds it in. I thought maybe an o-ring was out of place, as it is installed at a weird angle. I used some silicone lube to hold both o-rings in place (one on the block-off piece and one on the OEM DV housing) and reinstalled. Used high temp threadlocker on the DV bolts and tightened as much as possible, without breaking the plastic. Let the car sit for 18 hours just to be sure the threadlocker had time to cure.

Today there was no change in boost pressure (still 19 psi) and I threw the P0299 code again. I'm not sure what else to do. All of the pressurized piping I touched is tight, I also tightened the clamp on the hose coming off the throttle body (which I've never touched before), and I looked at the pipes between the turbo and intercooler, but they don't use normal worm gear hose clamps, they use some kind of clips so I don't think I can do anything with them.

I am a little concerned about the o-ring that seats in the ATP block-off piece, it is not very thick and doesn't protrude out of the machined groove around the whole circle. I figure it could be leaking slightly back into the intake side of the turbo, but it can't be escaping into the atmosphere due to the o-ring on the stock DV housing. I will try replacing that soon. Otherwise I am pretty much at a loss. I am running the stock intake, and I assume that most people who've gone Stage 2 already have aftermarket intake. Is it possible that the stock intake is too restrictive? Can anyone chime in that's running the stock intake on a chipped car? Specifically Stage 2? My other idea is that maybe the fuel pump is maxing out. However, I have not 'felt' a fuel cut, nor do I have Vag-Com so I can't log it. Would that throw a CEL? I will be getting Vag-Com in about a week, so I can check that then. Any other ideas?

Also, let me state that I do not think and do not mean to imply that this is a fault with APR's software. This issue obviously arose due to the increased requested boost pressure, but I think the at-fault component is something else on the car. Also this is not an intermittent issue, I have never seen more than 19 psi.

Thanks!


Modified by JaxACR at 12:41 AM 5-22-2008

[JaxACR]

Quick update: It's definitely not the intake being too restrictive, I pulled the filter out of the intake (I know, I know) and took spin. Still holding 19 psi.

I also checked the vacuum lines and tee to my boost gauge and SSQV, all of them are fine. Checked and tightened the vacuum tap that came with my VDO gauge and it seems fine. Also checked and tightened the MAP sensor in the throttle pipe, no change.

[staulkor]

If you have access to a compressor, do a pressure test. Get a 2" pcv end cap and put a quick connect on it and put it in the intake coupler on the turbo. Open the oil cap. Pressureize to 7psi or so using you boost gauge to measure it. Just listen for leaks and spray everything with soapy water. There will be a slight hissing coming from the head and maybe from the throttle body. Dont go much higher than 7psi though.

Also, log blocks 115 and 118 on vagcom. Just do a full 3rd gear pull from 2k-redline.

If there isnt an actual leak but it thinks there is, your MAP sensor could be going bad.

[MKV DarkstaR]

interesting, I'm curious as much as you are as to what the problem is that's throwing the code.

my assumption is vague butmaybe it's the SSQV / ATP block-off?
and from what I've read in your post, your still rockin' the stock DV as well? so there are 3 components? SSQV, stock DV, ATP block-off?

[JaxACR]

I don't have a compressor, but I'll ask around and see if I can find someone who will let me use theirs. I didn't even think about the map sensor, but it is entirely possible that it could have been damaged when I swapped the throttle pipe. Would the map sensor cause the car to run less boost? Because my boost gauge is showing 19 psi. I suppose if the map sensor was reading wrong it could be opening the wastegate too soon. I'll log with Vag-Com too, I'm probably going to order it tomorrow.

Regarding the DV setup, the ATP block-off plate replaces part of the stock DV. Basically you remove the rubber diaphragm and plunger from the DV, place the block-off plate in the hole on the turbo, and then put the top part of the stock DV (plastic piece with the electrical plug) over the block-off. This is done to hold the block-off in place and seals the hole with the DV's o-ring. Also, the stock DV harness is retained so that the car 'sees' the DV and does not throw a fault code, but it is not actually doing anything. It is unlikely that the SSQV is leaking, due to the design (the boost pressure holds it closed), but if all else fails I will throw the stock DV on to see if it helps. If I pull the block-off again, I will take a pic of it with the DV and also the DV assembled normally so it will make more sense.

Thanks for your responses! And on another note, does anyone know if the wastegate on the 2.0T is vacuum-actuated, or is it electronic like the stock DV?

[400gti]

Hi i know exactly what you going through.Just read my post which i had done a few weeks ago.I know im in South Africa and dont have access to much of the mods that is available to you guys.Anyway,read the thread that i had posted,and i can happily say that it is now 3 days since that code has been called up.Heres what i did:I fitted my forge dv back,i installed a forge intake And heres where i think the problem was-sensor in plastc throttle body housing.I removed it because i had basically checked everything.On removal,the sensor was covered in oil.I cleaned it out and put it back.I cant be 100% sure it was the fault caus i had done everything together.Let me know if there is anything else you need info on

[JaxACR]

Thanks for the tip! I will check it out. It is very possible that is my problem, because I've got oil in my intercooler hoses (who doesn't?) and when I pulled my air filter out last night I saw a couple of spots of oil on it, so obviously it is making it up to the MAP sensor. I'll check it out tomorrow.

Aside from that, I did drive about 75 miles today and the code hasn't come back! I actually pegged 20 psi once today too. I'm more than happy at 19 psi, I just hope this code doesn't come back!

[JaxACR]

Well I've put on another 45 miles or so in the last two days and still no CEL It has all been in high temps (90+ deg F), and the CEL seemed to mainly come on at night when it's cooler. I'll be out tonight so I'll try to get on it, but I think the issue has resolved somehow. Holding 18-19 psi still, but I'm happy.

[JaxACR]

CEL came on again today. I took the SSQV off and put the stock DV back on. Now it is hitting 23 psi with ease, it feels like getting chipped all over again. I think the o-ring on the block-off was the culprit, mainly because it was gone (probably hanging out in my intercooler somewhere in 1000 pieces. I took pics, but it's too late tonight. I'll upload them tomorrow.

Anyone know where I can find a beefy 1" diameter o-ring that will stand up to the heat of sitting right on the turbo?

[Angel@forgemotorsport.com]

Looks like you may have found it. Do you have access to vag com? be interesting to see the change between logs.

[MKV DarkstaR]

Quote, originally posted by JaxACR »

CEL came on again today. I took the SSQV off and put the stock DV back on. Now it is hitting 23 psi with ease, it feels like getting chipped all over again. I think the o-ring on the block-off was the culprit, mainly because it was gone (probably hanging out in my intercooler somewhere in 1000 pieces. I took pics, but it's too late tonight. I'll upload them tomorrow. Anyone know where I can find a beefy 1" diameter o-ring that will stand up to the heat of sitting right on the turbo?

see, I had a feeling it was the SSQV

[JaxACR]

Ok, here's the pics I promised.

Stock DV:

ATP block-off (top half of stock DV to holds it in place):

And finally, here is what's left of the O-ring that makes the seal between the block-off and the turbo housing :

Just to reiterate, I am certain that the SSQV itself was not leaking, it was this block-off piece. The fact that the O-ring (which is what actually makes the air-tight seal) was utterly obliterated reaffirms this.

EDIT: After looking at the pics again, I think I may have overlooked something. Does anyone know if the black ring (far left in the first pic) is supposed to be used in conjunction with the block-off piece? Perhaps leaving that out is what caused there to be enough wiggle room for the O-ring to become dislodged and, presumably, sucked through the turbo. The thing did not come with instructions.


Modified by JaxACR at 3:06 PM 5-29-2008

[syntrix]

Quote, originally posted by staulkor »

If you have access to a compressor, do a pressure test. Get a 2" pcv end cap and put a quick connect on it and put it in the intake coupler on the turbo. Open the oil cap. Pressureize to 7psi or so using you boost gauge to measure it.

Didn't we go down this road already?

If you tap into the turbo inlet, the rear pcv will allow flow. The pressure will just escape through the oil cap.

You also do NOT want to leave the cap on, as you will pressurize the crankcase. This is BAD.

K, carry on, it's your car.