1G BOV as stated, and the CEL is probably from running so rich. the 02 sensor is going crazy from all the un burnt fuel passing it… and if it were an ECU issue the car more than likely wouldnt run, the ecu issues are commonly a capacitor within the ECU goes bad
Definitely. But it helps a lot when it gets narrowed down. Like I said, I did a leak test and it wasn’t an obvious fail, nor did I hear any air escaping or see bubbles on my lines.
Replies as comprehensive as you guys provided help out a million times more.
I’ll post results as soon as I have them.
In my first post, I wasn’t being sarcastic in the sense that I didn’t believe them. I just wished they had given some more insight into the diagnosis.
The “boost leak” comment comes from a lot of people that just puke out what they have read and cannot explain what it is or how to fix it.
Since everyone else has hit on everything but this really, the 02 sensor fault will have been from the boost leak. Car thinks its burning at 14.7:1 (or w/e ratio the car uses) and so expects to see a value at the 02 sensor since that is the next sensor in line, car isn’t burning a 14.7:1 and the 02 sensor will read as such. Comp doesn’t know that so thinks the 02 sensor is reading faulty, throws the CEL.
This is correct but for most cars, it uses NB02 voltages and doesn’t know specific ratios.
Also, during CLOSE-LOOP operation, the ECU does not read 02 sensor input. It uses the MAF signal.
There’s another thing to bring up though, please correct me if I’m wrong. The MAF is what meters the air, right? If the 02 sensor fails to go into closed loop mode, could this send things out of wack as I described as well?
I believe engine load is what determines if you are open vs closed. I believe the parameters for that is the engine speed and the air flow sensor. I must be missing something as that is very simplistic. You could have leaky caps on your ECU or an issue with the MAF. The car runs fine during normal operation (light/mid throttle and idle), correct?
…exactly…pcm references load via RPM vs TPS on the old epprom and determine closed/open loop from that. O2 fault is definitely corellated to the leak. You’re probably running ~10.5 or lower on the AFR when the scenario occurs. That’ll trip a CEL for certain.
Repair the bypass issue first, then sort any sub issues after.
Ask Travis about that. 
Correct. It will bitch that it cannot maintain fuel trims or something similiar. Basically: “I cannot maintain stoich. You fail”.
Right now the car idles at ±1100 rpms with some surging at start up, it eventually evens itself out to 750, which is probably related to the problem. With the wastegate held open I can go through the entire power band with no issues. Without it held open, I can drive the car, just have to stay under 3k RPMs.
MAF was the first thing I tested. Car died when unplugged. So, I’m confident that it’s functioning right.
WG held open (WG pressure), car drives fine
WG not held open, boost spikes and car pukes smoke out the rear, and the BOV pukes all the air out? Does this occur with the car using the WG but at WG pressure (ie no MBC inline but just connecting a vacuum line directly to the turbo’s inlet).
You said the WG was replaced and it’s working fine so something is causing that BOV to release air but you pressure tested to 15PSI and it didn’t leak at all? BTW, I run 20-LOW 3X and I pressure test to 40PSI or so. I don’t run that boost but it’s easier to see leaks.
I replaced it with a known working one. I haven’t tried it out with the vacuum line from one tee to the other, I honestly can’t tell ya until I try that. Might not get around to it tonight, it’s pissing buckets out.
I’ll run another boost test at a higher psi. I just don’t want to overwhelm the stock system. I’ll also vac test the BOV while I’m at it.
If it’s not leaking at 15PSI, you are fine. I am just stating you should go higher to ensure you can see even the little leaks.
I am missing something. The BOV is definately opening during WOT operation which is a problem. I am not sure why you are not seeing this during pressure test. It’s like I forgot how shit works. 
please dont remind me… :sad
the surging at first start up is the ecu attempting to get a reading from the 02 sensors… once it cannot gain a stoichiometric reading it goes into pprom (pre programmed read only memory) and goes off set base values stored in the ecu that are KNOWN proper running values. it basically says " 02 sensor… you fuckin blow, im not listening to you."
have you attempted to flash any tunes to the ecu of some sort or have you fucked with an AFC or something like that? these things could also be causing running issues whether you have a properly functioning BPV or not. definitely fix the bypass valve first then move on to ecu controlled operations such as fueling and whatnot.
Wait. The car has fuel mods!?
Also, surging can be caused by other things.
i dont know if it has fuel mods or not… but the readings can and would be iffset if there were something such as an AFC in there that was fucked with… surging could possibly be a vacuum leak or something of the sort, but speaking from prior experience (trust me on this one shawn) the most likely culprit is the ecu saying “fuck you” to the 02 sensor and running on base values instead.
No fuel mods or piggybacks. I’m not even near the level where it is needed.
Only mods on the car are a K&N FIPK and the MBC.
Question-Are the Ebay ghetto BOVs reliable enough to use as a band-aid for now? I’ve called around to several boneyards and classifieds sites with no luck on a 1G BOV.
just save and buy things once kris… nothing worse than buying the same shit twice because u cheaped out the first time around.
Take the words straight from the horses mouth.
The ECM on this car doesn’t use the 02 sensor for determining open and closed loop? The air fuel mixture is determined through the 02 sensor. The ECM knows how much air is going into the engine through the MAF and how much fuel by the fuel pressure and PW of the injectors. And than uses the 02 sensor to fine tune from there, or is this car that much different than what I’m used to? Soon as the 02 sensor heats up enough to start switching it goes from closed loop to open? Ignoring other factors. Sorry for the very off topic tangent