kamnamurt Posted September 9, 2018 Share Posted September 9, 2018 Hello, My MPG for my legacy 3.0r have been going crazy, it would read anywhere from 2-10 Mpg while driving under normal conditions and when I come to stop or not on throttle it will still read a 30-70 mpg reading when its typically 100 since I am not driving. I have read that sometimes this is just an indicator but my real mileage have really been that bad. It also effects my idle and RPM, when the MPG gauge goes crazy you can also see the RPM interacts similarly. I have read that this may be my o2 sensors, I have also added roughly 7.8 quarters of oil, 1 quarter more than I am suppose to due to the bad readings I get from the dip stick and other information I have read on the forums. I am assuming this is not effecting it since this issue comes and goes. Please see the video as I am just driving through local streets and stops. Link to comment Share on other sites More sharing options...
relative4 Posted September 9, 2018 Share Posted September 9, 2018 Assuming your CEL is not on, you'll need live data to debug. Good options are an OBDLink dongle with the BtSsm Android app or a VAG-COM cable with the FreeSSM Windows app. Link to comment Share on other sites More sharing options...
Perscitus Posted September 10, 2018 Share Posted September 10, 2018 Yup BtSsm is your friend, else just speculation. But if you want some potential leads and to throw $$$ at the problem/s: Injectors, Spark plugs, Fuel pressure regulator, fuel filter/s, pre-filter sock, Front AF/Lambda sensor/s, Rear O2 sensor/s, primary cats, secondary cats, vaccuum leaks, exhaust leaks, etc. The instantaneous MPG indicator is just a dummy formula based calc that feeds off of a bunch of sensor data on the cars network bus, passed around from sensors to ECU, etc. and here - digested by your BIU. Even something such as a malfunctioning Throttle butterfly plate, DBW module, TPS can cause bogus output. Even when working its about as accurate as fakenews. Link to comment Share on other sites More sharing options...
Tronic Posted September 10, 2018 Share Posted September 10, 2018 Whats the millage and service history ? have you owned it long enough to know if the O2 sensors have been replaced ? Are you saying its using alot of oil ? Link to comment Share on other sites More sharing options...
Tronic Posted September 10, 2018 Share Posted September 10, 2018 The instantaneous MPG indicator is just a dummy formula based calc that feeds off of a bunch of sensor data on the cars network bus, passed around from sensors to ECU, etc. and here - digested by your BIU. Would not have thought so its just a calculation taken from the injector cycle and hence the ECU knows how much fuel your using and your current speed. Link to comment Share on other sites More sharing options...
Perscitus Posted September 10, 2018 Share Posted September 10, 2018 Yup, Fuel Learn/Correction, RPM, MAF g/sec, Load g/rev and Injector PW/DC Link to comment Share on other sites More sharing options...
covertrussian Posted September 10, 2018 Share Posted September 10, 2018 I don't see anything wrong here, it's just instantaneous MPG readout it will vary a lot based on driving conditions. As for fully stopped, it's basic math, you can't divide by zero... if your going 0mph you will get 0mpg. This is why you have to average the MPG to get meaningful numbers. 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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