Tmccurry Posted July 6, 2017 Share Posted July 6, 2017 This car just won't accept running correctly... My new issue is I went from 18-19mpg (based on driving style and route to work) down to 15.8mpg and dropping (no wot). The car has 102k miles with process west tmic, ID 1000cc too feed, walbro 255, Fp green, grimmspeed intake with box, Gfb respons, stock engine. Tuned by tuning alliance. All of the above mods have less than 6000 miles on them. Oil change was 2000 miles ago and not burning any noticeable amount of oil. I still have crazy roughness in cylinder 4 (0-100 continuous on the Cobb). Tuner doesn't seemed bother by it because of my actual knock count. I have done all the spark plug, fuel injector, coil swaps possible. Roughness stays cylinder 4. Compression test was 125 cylinder 4 and 128 cylinder 2. I believe I have a bad wheel bearing (new one arrives today). Could this kill gas mileage so much? Additionally, with the a/c on at a stop if I give a sharp rev, the car drops to ~500rpms and feels like it's going to stall (this could just be a bad compressor), not sure if it's a related issue. Doesn't happen with a/c off. Completely at a loss with this car right now. Ready to give up on the build Link to comment Share on other sites More sharing options...
GTEASER Posted July 6, 2017 Share Posted July 6, 2017 Front o2 sensor is bad and needs replacing, thus the bad gas mileage and a phantom misfire. GTEASER's 2012 Legacy GT - Sold GTEASER's 2009 XTeaser - Sold GTEASER's 1992 Legacy SS - Sold Stapp's Law: “The universal aptitude for ineptitude makes any human accomplishment an incredible miracle.” "Simple incompetence is a far more sinister force in the world than evil intent." Link to comment Share on other sites More sharing options...
Max Capacity Posted July 7, 2017 Share Posted July 7, 2017 The other day sitting in line at work waiting for my turn to leave I notice the idle would drop low with the AC on. If I rev'd it for a couple seconds it would idle normal. Mike has set my idle to 900rpm. I have been on Mike's tune for many years, he is that good. Use the front Denzo O2 we recommend in the sticky, http://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238.html 305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD). CHECK your oil, these cars use it. Engine Build - Click Here Link to comment Share on other sites More sharing options...
Tmccurry Posted July 7, 2017 Author Share Posted July 7, 2017 I have no idea why o2 never crossed my mind. I feel dumb. I honestly haven't paid any attention to the o2 sensor setup on this car. I'm assuming I have one in front of my wideband And I agree with your statement about Mike. Dude has been extremely helpful and patient with my million questions Link to comment Share on other sites More sharing options...
xt2005bonbon Posted July 7, 2017 Share Posted July 7, 2017 I still have crazy roughness in cylinder 4 (0-100 continuous on the Cobb). Do you feel the misfires? When does this occur? Idle only or at any driving condition? If it goes from 0-100 non stop, then that's a pretty serious misfire. This happened to me before when one of my injectors was not sitting properly and was dumping too much fuel. Cat glowed red Link to comment Share on other sites More sharing options...
JmP6889928 Posted July 7, 2017 Share Posted July 7, 2017 Front o2 sensor is bad and needs replacing, thus the bad gas mileage and a phantom misfire. This would be my first guess too. Rarely do they even set CEL when they go bad but all kinds of issues come from the failure. Find someone you know with a known good O2 sensor and change it and see if all of the issues go away. My guess is that it will make a huge difference. Link to comment Share on other sites More sharing options...
GTEASER Posted July 7, 2017 Share Posted July 7, 2017 In the '05, the front o2 sensor is in the up pipe, right? GTEASER's 2012 Legacy GT - Sold GTEASER's 2009 XTeaser - Sold GTEASER's 1992 Legacy SS - Sold Stapp's Law: “The universal aptitude for ineptitude makes any human accomplishment an incredible miracle.” "Simple incompetence is a far more sinister force in the world than evil intent." Link to comment Share on other sites More sharing options...
Moderators BarManBean Posted July 7, 2017 Moderators Share Posted July 7, 2017 In the '05, the front o2 sensor is in the up pipe, right? EGT is in the up pipe. Front O2 is in the exhaust manifold just below the up pipe. "Bullet-proof" your OEM TMIC! <<Buy your kit here>> Not currently in stock Link to comment Share on other sites More sharing options...
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