solidxsnake Posted September 4, 2019 Share Posted September 4, 2019 Hm. I don't see any documentation on that parameter in the Cobb documentation. I wonder what it's actually supposed to mean. Does it change at higher RPM/load? Is your car tuned pure SD, or is it tuned hybrid MAF/SD? If the latter, I wonder if that's just a meaningless number since it's outside of the range that SD tuning is active. Link to comment Share on other sites More sharing options...
gkinslow Posted September 4, 2019 Author Share Posted September 4, 2019 Definitely not receiving any information from the MAF sensor. %100 speed density. And no it didn't change even under medium/ high amounts of boost. I emailed Cobb and they replied that I should be looking at the Manifold absolute pressure parameter. I guess I'll take another log including that. Really hoping my tuner can make time to take a look at the logs, but it's race season still so who knows. No response from AEM technical department. Link to comment Share on other sites More sharing options...
gkinslow Posted September 4, 2019 Author Share Posted September 4, 2019 Tuner said it was the Manifold reference hose coming off of the BPV. Definitely not that. Pulled it, reseated, reclamped it..... No change. His only other guess was the lower fuel injector seals. He whatever the issue is (leak) has to be after the throttle body to raise the rpm like it is. Currently spraying brake cleaner and watching the AFR Link to comment Share on other sites More sharing options...
gkinslow Posted September 9, 2019 Author Share Posted September 9, 2019 After 3/4 of the largest can of brake fluid I've ever seen, I still can't find a leak. Assuming the tuner is right and there's a post throttle vacuum leak... I'm wondering if the BPV could be leaking internally and causing my vacuum leak? Cobb XLE BPV version 2. Link to comment Share on other sites More sharing options...
solidxsnake Posted September 9, 2019 Share Posted September 9, 2019 BPV is pre-throttle, though. I assume you've checked the mainfold/TGV housing and TGV hosuing/head connections with the brake cleaner. this sounds like a sensor problem to me, personally. Link to comment Share on other sites More sharing options...
gkinslow Posted September 9, 2019 Author Share Posted September 9, 2019 Yes I checked all those places with the brake cleaner (and basically anything attached to the intake manifold) and the AF ratio never varied more than .5 The reference line from BPV to manifold is post throttle body... no? Not the large recirc line. They make a rebuild kit for the XLE BPV. For $15 its worth a shot. Tuner "ruled out" the MAP sensor saying "the MAP sensor doesn't affect idling, only fueling" I don't know what other sensor would be involved. APP, TPS, front o2 have all been replaced. TiC wants my to bring it up there and were basically zero help when I contacted them. My ebay bought smoke maker couldn't hold <10psi so I'll be constructing my own but the car passes the "block intake and blow into the BPV reference line" test. Link to comment Share on other sites More sharing options...
solidxsnake Posted September 9, 2019 Share Posted September 9, 2019 The reference line from BPV to manifold is post throttle body... no? Ah yes, that's correct. I thought you meant the bypass line itself. Still, the symptoms seem more feedback/computer related than mechanical to me. Link to comment Share on other sites More sharing options...
gkinslow Posted September 9, 2019 Author Share Posted September 9, 2019 I'm totally with you there, but I cannot seem to find a parameter I can log that is out of whack enough to point me at a particular sensor. At this point the only 2 possibly relevant sensors I haven't changed would be the MAP, the rear O2, and the IAT. I can't see the IAT causing it and it looks to be accurate anyway. I'd be shocked if it was the ECU and everything was this normal under load and only a problem when this system is trying to pull a vacuum. (at idle speeds) So I'm trying to follow the "professional" advice of the well known tuner over my own assumption at this point. I'll blow the $15 on the rebuild kit for the BPV, and I have a replacement for the BPV reference line already on the way. I'm no ready to give up and tow it to TiC just yet. Even though it needs to go up there and have the FF kit installed and tuned anyway. Figuring out this issue is a pride thing at this point. Link to comment Share on other sites More sharing options...
ehsnils Posted September 9, 2019 Share Posted September 9, 2019 How about the brake booster or PCV valve? Link to comment Share on other sites More sharing options...
gkinslow Posted September 9, 2019 Author Share Posted September 9, 2019 How about the brake booster or PCV valve? I thought of the brake booster but can really only access the brake booster end of that hose, and it's definitely secure. I'll be able to test more definitively once my home made smoker is finished. I'm seriously disappointed my eBay smoker couldn't even hold 5-8psi. I've also zip tied every vacuum line that wasn't already. (that I can get to without removing the manifold) Link to comment Share on other sites More sharing options...
ehsnils Posted September 11, 2019 Share Posted September 11, 2019 Just try to plug the brake booster hose and see if that makes a difference. Only side effect is that you have to push the brake pedal harder. Link to comment Share on other sites More sharing options...
gkinslow Posted September 11, 2019 Author Share Posted September 11, 2019 The Cobb BPV rebuild kit and new OEM BPV/manifold reference line are sitting on my front porch according to UPS tracking. I'll try plugging the brake booster, replacing the reference line, and rebuilding the BPV today. Link to comment Share on other sites More sharing options...
gkinslow Posted September 13, 2019 Author Share Posted September 13, 2019 Well, definitely not the BPV or brake booster leaking internally. Gathered the rest of my materials to build a better smoke maker. Will attempt round 3 of smoke testing this weekend. Link to comment Share on other sites More sharing options...
gkinslow Posted September 25, 2019 Author Share Posted September 25, 2019 Ater another smoke test and a bunch of research on NASIOC I'm throwing in the towel. Car is going to TiC whenever I can arrange the 100 mile tow for some general maintenance and flex fuel instal/ retune. (Assuming this issue isn't something stupid) Link to comment Share on other sites More sharing options...
ehsnils Posted September 28, 2019 Share Posted September 28, 2019 Then what I'm thinking of is a wonky cam or crank sensor, if one of them isn't well then you'd get strange effects too. Link to comment Share on other sites More sharing options...
gkinslow Posted September 30, 2019 Author Share Posted September 30, 2019 I started wondering if the alternator could be an issue. (asking for increased RPM due to a drop in voltage) Grasping at straws here. Also found a very similar issue with a less modified WRX that ended up having the ECU patched by the dealership. NASIOC had all kind of threads with very similar issues, all with different "solutions" It is odd to me that the moment the "blue light" on the temp guage goes off the RPM drops down to a normal idle speed. TiC is booked until the 14th of next month, but I'll update this when/if I ever have a definitive answer. Link to comment Share on other sites More sharing options...
ehsnils Posted October 1, 2019 Share Posted October 1, 2019 If this coincides with the blue light then it might be that your temperature sensor isn't behaving correctly so that the ECM thinks it's colder than it is and then when the sensor gets warm then it's starting to work correctly. Not sure about the price of that sensor or where it's located, but it should be relatively cheap. Link to comment Share on other sites More sharing options...
gkinslow Posted October 1, 2019 Author Share Posted October 1, 2019 I considered that as well but it doesn't disappear completely after warming up. The rpms still surge when shifting gears and that can't be temp related. Link to comment Share on other sites More sharing options...
ehsnils Posted October 2, 2019 Share Posted October 2, 2019 I hope that you have tried with the AC off, since when the compressor is on the idle is adjusted. Link to comment Share on other sites More sharing options...
gkinslow Posted October 2, 2019 Author Share Posted October 2, 2019 I only drive the car evenings and weekends so normally I don't use the AC. I prefer the sound of the exhaust with the windows down. I'm really hoping the tuner is right and it is just a post throttle body leak that I cannot chase down with my inferior leak testing. Link to comment Share on other sites More sharing options...
ehsnils Posted October 4, 2019 Share Posted October 4, 2019 Another thing that can lead to strange issues is a ground fault. Link to comment Share on other sites More sharing options...
gkinslow Posted October 30, 2019 Author Share Posted October 30, 2019 Partial update: The car has been at TiC for a couple days now. It has confounded them much like it did me. (makes me feel slightly better about not figuring it out) It passed a leak down test and they found a couple very small boost leaks. They are going to clear those up, do some suspension work, and look at the main issue when the tuner is in the building. Assuming they can figure the issue out, we will then have to send my Holy Headers off to Killer B so they can modify the UP for EWG. They refused to sell me an EWG UP separately, so this will take a couple more weeks. Then install the EWG, FF kit, and finally re-tune. Link to comment Share on other sites More sharing options...
gkinslow Posted November 12, 2019 Author Share Posted November 12, 2019 Finally have a resolution to this issue. (for the 2 people still subscribed) Barometric pressure sensor failure. It was reading the minimum always and therefore incorrectly compensating for it at idle. Thanks for all the suggestions and help with the troubleshooting. I feel better knowing that it took TiC multiple weeks to figure out as well and I'm not a complete failure as a backyard mechanic. Link to comment Share on other sites More sharing options...
Nonamedude Posted November 12, 2019 Share Posted November 12, 2019 That's the MAP sensor right? The one with the funky white circle on it? Did they say how they tracked it down finally? Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
gkinslow Posted November 12, 2019 Author Share Posted November 12, 2019 Negative. Not the MAP sensor. It's a part of the secondary air injection pump on the post-facelift models. (Not sure where barometric pressure is calculated on pre-facelift.) The tuner started digging and eventually looked at the barometric pressure (after ruling out EVERYTHING else) and realised it was defaulting to the lowest reading. He has tuned thousands of Subarus and said he's never seen this. Not once. Link to comment Share on other sites More sharing options...
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