adj789 Posted February 19, 2014 Author Share Posted February 19, 2014 How's your O2 sensor(s)? Mine shakes quite a bit and my mileage is shit, but that's also because my O2 isn't sending a proper signal (Have CEL, though), so I'm sure it's not fueling right. (Read: dumping fuel) I'd seriously consider investing in a Cobb AP if you haven't already. You're clearly gonna dump more money into the car anyway -- You can find 'em used on CL, or new from Cobb for about $650. And having the ability to base tune, plus pull codes and run multiple maps -- it's the best money you can spend on your car. I had the 02 sensors replace when I put my exhaust on, they should be fine but I had the issue before they were put on. I'd love to get an AP, not in the budget right now Link to comment Share on other sites More sharing options...
rob-2 Posted February 19, 2014 Share Posted February 19, 2014 I had the 02 sensors replace when I put my exhaust on, they should be fine but I had the issue before they were put on. I'd love to get an AP, not in the budget right now Buy a usb to obdII cable and load romraider on your laptop. $20 solution vs $650 if you want to see what is happening with your motor via it's sensors. Link to comment Share on other sites More sharing options...
covertrussian Posted February 20, 2014 Share Posted February 20, 2014 It shouldn't improve MPG. It might cut down on oil use if stuck. There was another guy in this thread that mentioned around 4mpg gains. It actually makes sense... if it's stuck open, boost will go into the crankcase and cause resistance for pistons. If it's stuck closed you are not sucking in the fuelly blow by that can be reburned, with a properly working O2 sensor that should cut back how much fuel is injected aka better mpg. Buy a usb to obdII cable and load romraider on your laptop. $20 solution vs $650 if you want to see what is happening with your motor via it's sensors. This, for just datalogging opensource all of the way. If you plan on reflashing it, get a Tactrix cable ($150), they are known to 100% work. 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
stealitall Posted February 21, 2014 Share Posted February 21, 2014 Could the O2 sensor stop working and not throw a CEL? Link to comment Share on other sites More sharing options...
jeffy2.5xt Posted February 21, 2014 Share Posted February 21, 2014 no it cant. the o2 goes even off a little it will give you a light. Link to comment Share on other sites More sharing options...
rob-2 Posted February 21, 2014 Share Posted February 21, 2014 There was another guy in this thread that mentioned around 4mpg gains. It actually makes sense... if it's stuck open, boost will go into the crankcase and cause resistance for pistons. If it's stuck closed you are not sucking in the fuelly blow by that can be reburned, with a properly working O2 sensor that should cut back how much fuel is injected aka better mpg. This, for just datalogging opensource all of the way. If you plan on reflashing it, get a Tactrix cable ($150), they are known to 100% work. I'm not meaning to start a debate but it would have to be a massive amount of pressure to change 4mpg on 20mpg. You're talking about a 25% decrease over a pressure change. I can also tell you that while I had a completely stuck PCV and low comp in cycl 2 and 4. I still got the same MPG. The ECU isn't correcting for resistance on the cyl. It's putting in the A/F ration it's programmed too. PVC is strictly emissions related. Link to comment Share on other sites More sharing options...
covertrussian Posted February 21, 2014 Share Posted February 21, 2014 Could the O2 sensor stop working and not throw a CEL? no it cant. the o2 goes even off a little it will give you a light. Actually yes it can. When I did my uppipe install I killed my front O2 sensor (my own stupidity), city driving no cel's all was well. As soon as I started going 60mph for more then 5 miles Cruise would start flashing but still no cel. I would turn off the car, start it and cruise flashing was gone. Best way to know if your O2 sensor is having issues is wideband.... I'm not meaning to start a debate but it would have to be a massive amount of pressure to change 4mpg on 20mpg. You're talking about a 25% decrease over a pressure change. I can also tell you that while I had a completely stuck PCV and low comp in cycl 2 and 4. I still got the same MPG. The ECU isn't correcting for resistance on the cyl. It's putting in the A/F ration it's programmed too. PVC is strictly emissions related. Your right it's not THAT much, though if they did a lot of mountain driving, you would be in boost a good bit. 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
Xplosivo1 Posted February 22, 2014 Share Posted February 22, 2014 I read today that Cobb very recently released some new software that will allow you to dial in an accurate MPG readout even with bigger injectors when using their ProTuner software. Can you post a link? This is something I want to get corrected, not so much for accurate MPGs but for how far I can go in what I have left in the tank. Link to comment Share on other sites More sharing options...
JmP6889928 Posted February 22, 2014 Share Posted February 22, 2014 Could the O2 sensor stop working and not throw a CEL? ABSOLUTELY it can. It can cause STFT and LTFT to go all over the place and never set a code or CEL (ask me how I know this) and will make you search a lot of other things that are fine. Also, purchase an OE O2 sensor if you do decide to replace it as the aftermarket ones don't seem to hold up (again, ask me how I know this-stinking NTK) and they're not any less expensive anyway. If you can find someone close to you that has a known good front O2 sensor, change it out and try the car and I'll bet you see a difference in how the car runs as well as MPG. If not, then perhaps you'll need to go in via opensource or romraider, but I would place my money on the front O2. I've seen it fix about a dozen cars that had weird fueling and driveability issues and IIRC, only one of them had a CEL on with a hard code for O2 failure. Link to comment Share on other sites More sharing options...
adj789 Posted February 22, 2014 Author Share Posted February 22, 2014 Just threw a CEL pulling into work, not sure what it could be car feels the same. I can't get it checked til Monday. Link to comment Share on other sites More sharing options...
BoozeRS05 Posted February 23, 2014 Share Posted February 23, 2014 You can read a CEL at anytime, by yourself, with no additional tools. Your car has an onboard diagnostic code reader, all 05 LGTs have them. EB's Subaru journal - 2005 LegacyGT Wagon & 2014 Forester FB25 (2008 specB - RIP) IG@legacygtliving Link to comment Share on other sites More sharing options...
adj789 Posted February 23, 2014 Author Share Posted February 23, 2014 Misfire on cyl 2 **** Link to comment Share on other sites More sharing options...
covertrussian Posted February 24, 2014 Share Posted February 24, 2014 Bad plugs or bad coil pack, there is your MPG issue. 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
adj789 Posted February 24, 2014 Author Share Posted February 24, 2014 I just had them replaced Link to comment Share on other sites More sharing options...
covertrussian Posted February 24, 2014 Share Posted February 24, 2014 What brand plugs and what brand coil packs? 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
adj789 Posted February 24, 2014 Author Share Posted February 24, 2014 Not sure what brand plugs but they were platinum, he did show me the pack the coils came in to show they were performance brand (forgot the name) but I will ask them tomorrow, regardless I was having this issue before they were replaced and it didn't help. Link to comment Share on other sites More sharing options...
covertrussian Posted February 24, 2014 Share Posted February 24, 2014 Make sure they are NGK's and not Autolites or especially Bosch's. As for coils, my general rule of thumb is, all electrical components need to be OEM, aftermarket just horribly fails in this area. Did you check your compression btw? 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
rob-2 Posted February 24, 2014 Share Posted February 24, 2014 Have you logged you a/f while driving? Link to comment Share on other sites More sharing options...
adj789 Posted February 25, 2014 Author Share Posted February 25, 2014 The coil was bad, they replaced it for free. The plugs are NGK iridium. I'm gonna hold off for now on the compression test and see how it runs. For now it's running great. I'm going to get a cable next week for data logging. Link to comment Share on other sites More sharing options...
BoozeRS05 Posted February 25, 2014 Share Posted February 25, 2014 Nice, hopefully there's a light at the end of the tunnel for you soon. Way to stick through it. EB's Subaru journal - 2005 LegacyGT Wagon & 2014 Forester FB25 (2008 specB - RIP) IG@legacygtliving Link to comment Share on other sites More sharing options...
rob-2 Posted February 25, 2014 Share Posted February 25, 2014 The coil was bad, they replaced it for free. The plugs are NGK iridium. I'm gonna hold off for now on the compression test and see how it runs. For now it's running great. I'm going to get a cable next week for data logging. compression won't drive down MPG, just keep that in mind. Link to comment Share on other sites More sharing options...
adj789 Posted February 25, 2014 Author Share Posted February 25, 2014 compression won't drive down MPG, just keep that in mind. but an air leak would right? Link to comment Share on other sites More sharing options...
adj789 Posted February 25, 2014 Author Share Posted February 25, 2014 Nice, hopefully there's a light at the end of the tunnel for you soon. Way to stick through it. I really like this car. The only thing I need now is better tires, right now it has shitty Falkens. Link to comment Share on other sites More sharing options...
rob-2 Posted February 25, 2014 Share Posted February 25, 2014 but an air leak would right? Not usually no. An air leak won't change the ECU's target A/F like a bad 02 sensor will. Link to comment Share on other sites More sharing options...
covertrussian Posted February 26, 2014 Share Posted February 26, 2014 compression won't drive down MPG, just keep that in mind. Low compression = leak somewhere = air and fuel mixture escaping during the compression stroke & inconsistent combustion rates between cylinders = Less efficient per cycle http://www.youfixcars.com/engine-compression-test.html 05 LGT 16G 14psi 290whp/30mpg (SOLD) 12 OBP Stock 130whp/27mpg@87 Oct 00 G20t GT28r 10psi 250whp/36mpg 22 Ascent STOCK Link to comment Share on other sites More sharing options...
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