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Old 11-08-2013, 09:45 PM   #1
kericks06
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Default Fuel Issues

Hey guys I have an 07 sti and I just recently purchased this vehicle.. I have noticed that I can drive about 15 miles with a new tank of gas and it already moves well off of a full tank. After using about 1/4 of a tank I can go about 40 miles.. After 3/4 of a tank I had only gone 170 miles which is absolutely absurd.. Can anyone tell me what the causes might be? I have taken it to my subaru dealership and they seem to be a bunch of clowns. Twice now they have had no answer for me. I filled it up from 1/4 of a tank and it put in 11 gallons at 40.00 so I know its not the fuel gauge. I really need some help or this car will be sent right back please help
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Last edited by kericks06; 11-08-2013 at 09:51 PM.
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Old 11-08-2013, 09:56 PM   #2
the suicidal eggroll
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Ignore your fuel gauge...what's your actual mpg and we can go from there? If you don't know how to calculate mpg, then go punch your middle-school math teacher in the face.
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Old 11-08-2013, 10:07 PM   #3
kericks06
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Well I went 150 miles and it got me to 1/4 of a tank. I then filled it up and it took 11 gallons. So my math teacher would tell me that is 13.63 mpg. Mind you I have been babying this car and not driving like a fool. I am talking coasting in neutral a lot of the time etc.. I understand the tank on these is like 14.9 but is the fuel economy really that ****ty? I mostly saw people getting well into the 200s.. idk am I way off the mark on this?
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Old 11-08-2013, 10:14 PM   #4
mbhammerbro
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DGM

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Quote:
Originally Posted by kericks06 View Post
Well I went 150 miles and it got me to 1/4 of a tank. I then filled it up and it took 11 gallons. So my math teacher would tell me that is 13.63 mpg. Mind you I have been babying this car and not driving like a fool. I am talking coasting in neutral a lot of the time etc.. I understand the tank on these is like 14.9 but is the fuel economy really that ****ty? I mostly saw people getting well into the 200s.. idk am I way off the mark on this?
That seems crazy low. Any mods on the car?
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Old 11-08-2013, 10:18 PM   #5
kericks06
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Just an SRI and Cobb stage 1 tune. That is what I thought. Car runs actually fine, no noticeable problems. However this fuel problem is making pull my hair out.
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Old 11-08-2013, 10:28 PM   #6
the suicidal eggroll
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Quote:
Originally Posted by kericks06 View Post
Well I went 150 miles and it got me to 1/4 of a tank. I then filled it up and it took 11 gallons. So my math teacher would tell me that is 13.63 mpg. Mind you I have been babying this car and not driving like a fool. I am talking coasting in neutral a lot of the time etc.. I understand the tank on these is like 14.9 but is the fuel economy really that ****ty? I mostly saw people getting well into the 200s.. idk am I way off the mark on this?
Typical mixed city/highway mileage will be in the low 20's, yours is abnormally low. You mentioned that you have a Cobb stage 1 tune...time to make a log.

You need to log the following parameters for a typical drive (doesn't need to be long, just needs to cover the idle and cruise range):
DAM
Feedback KC
Learned KC
AFR Correction
AFR Learned
Target AFR
Actual AFR


Note that the above parameters are my names for them, not necessarily Cobb's names. You should find the most applicable field and log that (for example: "Learned KC" may be called "Fine Learning Knock Correction" in Cobb's software, you'll need to make some judgement calls here).

Usually problems like this are caused by an o2 sensor failure. If that's the case you should see abnormally high AFR Learned values (-5 to 5 is normal, outside of that typically indicates a long term fueling problem).
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Old 11-08-2013, 10:34 PM   #7
kericks06
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Ok I will do a data log then I will post it on here.
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Old 11-08-2013, 10:54 PM   #8
kericks06
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Since I can't upload a file how can I get you the data log?
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Old 11-08-2013, 11:00 PM   #9
the suicidal eggroll
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google docs, copy-paste, whatever you need.
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Old 11-08-2013, 11:06 PM   #10
kericks06
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Well it won't let me copy and paste because it is too long..
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Old 11-08-2013, 11:25 PM   #11
kericks06
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Can I email you the document?
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Old 11-08-2013, 11:47 PM   #12
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the data log, I let the car idle, normal driving, then I did a WOT 1st and 2nd Gear.

Last edited by kericks06; 11-09-2013 at 12:21 AM.
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Old 11-08-2013, 11:47 PM   #13
the suicidal eggroll
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If you like, I'll then put the document on my server.
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Old 11-08-2013, 11:49 PM   #14
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the data log, I let the car idle, normal driving, then I did a WOT 1st and 2nd Gear.

Last edited by kericks06; 11-09-2013 at 12:15 AM.
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Old 11-08-2013, 11:50 PM   #15
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the data log, I let the car idle, normal driving, then I did a WOT 1st and 2nd Gear.

Last edited by kericks06; 11-09-2013 at 12:20 AM.
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Old 11-08-2013, 11:51 PM   #16
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the data log, I let the car idle, normal driving, then I did a WOT 1st and 2nd Gear.

Last edited by kericks06; 11-09-2013 at 12:20 AM.
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Old 11-08-2013, 11:52 PM   #17
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the data log, I let the car idle, normal driving, then I did a WOT 1st and 2nd Gear.

Last edited by kericks06; 11-09-2013 at 12:20 AM.
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Old 11-09-2013, 12:53 AM   #18
kericks06
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Sorry I didn't mean to spam, it won't let me delete the old posts so I just copied and pasted the data log over them. Let me know what you see.
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Old 11-11-2013, 06:52 PM   #19
kericks06
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Anyone?
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Old 11-11-2013, 07:49 PM   #20
mbhammerbro
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DGM

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Check the link to datalog again. Can't view it. Make sure its public.
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Old 11-14-2013, 07:52 PM   #21
kericks06
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https://docs.google.com/spreadsheet/...FE&usp=sharing

That is the new link that is Public. I took the car in yet again and they said everything is normal.. I just don't believe that my car is ok getting 11mpg when im driving very lightly and getting about 90 miles to half a tank, just doesn't add up.
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Old 11-14-2013, 09:00 PM   #22
904svo
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Trying to get my kit car to pass ODB2 testing. (Cansiter test) What I found
was Subaru uses 2 gas tank senders which measure the EMPTY SPACE in the gas tank and send the correct voltage to the ECU to run the test, but
the gas gauge uses a stepper motor and can be off up to a 1/4 tank. It only reads the correct level at 1/2 and E. This is what I found out testing.

After I found this out I corrected my sender circuit and now pass the canister test.
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