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