blongo804 Posted December 21, 2010 Share Posted December 21, 2010 EDIT: just realized my dumb phone made the subject U2 sensors... Hey everyone, I have two quick questions. What should my O2 sensors be reading in my '05 LGT? When we plug in the OBD2 scanner, it only shows 2 O2 sensors operating. I thought there was 3? We're just still trying to figure out my 9.3-9.9 city mpg and this is basically what it has come down to. Any help is greatly appreciated! Link to comment Share on other sites More sharing options...
blongo804 Posted December 21, 2010 Author Share Posted December 21, 2010 Hopefully someone can help out.. Bump. Link to comment Share on other sites More sharing options...
StoplightAssassin Posted December 21, 2010 Share Posted December 21, 2010 HELLOOOOO! HELLOOOOOO! YEAH! YEAH! YEAH! YEAH! LGTs have two 02 sensors. There is one in the passenger side exhaust manifold and one in the downpipe. The sensor in the up pipe is an EGT. Your 02 sensors (AFRs) should read around 14.7 depending on tune. Anymore is getting lean and less is heading rich. Link to comment Share on other sites More sharing options...
TRSCobra Posted December 21, 2010 Share Posted December 21, 2010 There are only 2. One in the manifold on the passenger side, one in the DP. IIRC, the only one that matters for driveability is the first one. Link to comment Share on other sites More sharing options...
forayzor Posted December 21, 2010 Share Posted December 21, 2010 upstream 02 sensors (before cat) should be fluctuating from around .2volts to .8 volts, should have a wave pattern. downstream should be pretty steady. if downstream is fluctuating with the upstream, it indicates a bad catalyst. Link to comment Share on other sites More sharing options...
blongo804 Posted December 21, 2010 Author Share Posted December 21, 2010 Haha thank you for the U2 song! Hmm.. Well during our read, one was fluctuating under a volt and one was at 2.7 volts. I forget which is which but I assume the 2.7 one is not correct? I'm on a stock tune so should they really be reading 14.7? Link to comment Share on other sites More sharing options...
StoplightAssassin Posted December 21, 2010 Share Posted December 21, 2010 14.7 is the perfect balance between air and fuel. Conservative factory tunes are lower (richer) than that to err in the side of engine safety and longevity. Link to comment Share on other sites More sharing options...
blongo804 Posted December 21, 2010 Author Share Posted December 21, 2010 So would I have to tune it to 14.7 or it should come that way factory? Because both O2 sensors are reading much lower than that, as i've posted. Link to comment Share on other sites More sharing options...
StoplightAssassin Posted December 21, 2010 Share Posted December 21, 2010 what are you using to read it Link to comment Share on other sites More sharing options...
TRSCobra Posted December 21, 2010 Share Posted December 21, 2010 14.7:1 (stoichiometric) the ratio of air to fuel for ideal combustion. O2 sensors only have a certain voltage range that is much lower than 14.7 volts. Narrow band sensors cycle from 0.2-0.8 volts. That's a constant back and forth during idle. I think the front sensor is a wideband, though; I'm not sure on how those guys work. Link to comment Share on other sites More sharing options...
blongo804 Posted December 21, 2010 Author Share Posted December 21, 2010 We're using an OBD2 scanner and using it while I drive. Thanks for the info TRS, i'll tell my dad about it. (he's the mechanic here lol) Link to comment Share on other sites More sharing options...
TRSCobra Posted December 21, 2010 Share Posted December 21, 2010 Just found this page. Good read: http://www.picoauto.com/applications/lambda-sensor.html Link to comment Share on other sites More sharing options...
blongo804 Posted December 22, 2010 Author Share Posted December 22, 2010 Thanks a lot for the link! My dad found it handy. We're going to do more testing thursday when i'm off work/school so i'll post back then. We're pretty sure it needs a new O2 sensor..especially at 8.4 city mpg... Link to comment Share on other sites More sharing options...
blongo804 Posted December 23, 2010 Author Share Posted December 23, 2010 Well, did some more testing today and O2 sensors are running fine. We called the Subaru dealership and they gave me a whole bunch of crap. "Subaru's get bad mileage in the winter". Oh ok, that's why my brother's WRX stage 2 is up around 18 city and my friend Keith's LGT is getting 16-18 at stage 2.5 I believe it is. So what explains my STOCK LGT 8.4 mpg city? That is a mystery. Link to comment Share on other sites More sharing options...
Heedz Posted December 23, 2010 Share Posted December 23, 2010 lol u2 sensors back in the cold war eh? Link to comment Share on other sites More sharing options...
TRSCobra Posted December 23, 2010 Share Posted December 23, 2010 Dumb question, but are you warming your car up in the morning? Does it seem to have the power that it should? Link to comment Share on other sites More sharing options...
blongo804 Posted December 23, 2010 Author Share Posted December 23, 2010 I warm it for about 5 minutes in the morning. It definitely has power that it feels like it should have stock. Could my ~2000 mile shortblock/turbo be it? Is there some sort of break in that I don't know about? Link to comment Share on other sites More sharing options...
TRSCobra Posted December 24, 2010 Share Posted December 24, 2010 Are you getting any bad smells/black smoke from your exhaust? How about your oil, does it have a strong gasoline smell? I can't believe you're getting gas mileage that bad with a stock setup. Link to comment Share on other sites More sharing options...
blongo804 Posted December 24, 2010 Author Share Posted December 24, 2010 None of the above. Trust me, I can't believe it either. Link to comment Share on other sites More sharing options...
TRSCobra Posted December 24, 2010 Share Posted December 24, 2010 If I were you, I'd just get an aftermarket DP and a stage 2 protune. That would probably change your mileage for the better! Seriously. It couldn't hurt. Link to comment Share on other sites More sharing options...
blongo804 Posted December 24, 2010 Author Share Posted December 24, 2010 I really got to. I actually already have my CNT catted DP ready for install but i'm waiting for this crappy PA weather to go away and installing in the spring. You know how it is here.. Link to comment Share on other sites More sharing options...
TRSCobra Posted December 24, 2010 Share Posted December 24, 2010 The longer you wait, the harder it will be to get those DP bolts off! I hope you've got a catless UP, too. Link to comment Share on other sites More sharing options...
blongo804 Posted December 24, 2010 Author Share Posted December 24, 2010 They were actually just recently off after we put a new shortblock in. Yes, the catless UP will definitely be coming. Not trying to deal with cat failure there..that's all I need. Haha! Link to comment Share on other sites More sharing options...
TRSCobra Posted December 24, 2010 Share Posted December 24, 2010 Anti-seize is your friend in NEPA. Your BEST friend! You and Keith need to race when you get tuned! Link to comment Share on other sites More sharing options...
blongo804 Posted December 24, 2010 Author Share Posted December 24, 2010 Haha! I hear ya. My dad told me about that before I think. Me and Keith can definitely go at it when all his done. He'll just have to pick the legal place because I have no clue where any are. Link to comment Share on other sites More sharing options...
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