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Old 11-25-2006, 03:10 PM   #1
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Default 15 mpg: Halp

So heres the situation:

Walbro 190 goes in with 1.8 injectors.. gas mileage drops but isnt TERRIBLE (23mpg). 305s go in, 15mpg. Something just seems terribly wrong beyond normal fuel tuning. The CELs were some ground problem.. and an O2 problem, which was flicking on and off. In an effort to resolve this problem I grabbed an O2 off braineacks old motor which did not solve the problem (23 mpg), and in a further effort I got a brand new bosch o2 from advanced auto (like 20 bucks) which has me at my current 15 mpg. This is running roughly 10 psi @ 105 psi fuel .. 35ish idle psi fuel. To me it sounds ALOT like an o2 problem

Here comes the questions:

My mechanic buddy said I should try an OEM o2 (240 bucks ...uh no) because the standard 20 dollar o2 is probably not handling it right. Is there a real difference between splicing that o2?

Does anyone have any suggestions ?
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Old 11-25-2006, 03:28 PM   #2
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Sounds like a right foot problem.

Do you have a wb to monitor afr in the exauhst? I am always better than 25 mpg.


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Originally Posted by Newbsauce View Post
So heres the situation:

Walbro 190 goes in with 1.8 injectors.. gas mileage drops but isnt TERRIBLE (23mpg). 305s go in, 15mpg. Something just seems terribly wrong beyond normal fuel tuning. The CELs were some ground problem.. and an O2 problem, which was flicking on and off. In an effort to resolve this problem I grabbed an O2 off braineacks old motor which did not solve the problem (23 mpg), and in a further effort I got a brand new bosch o2 from advanced auto (like 20 bucks) which has me at my current 15 mpg. This is running roughly 10 psi @ 105 psi fuel .. 35ish idle psi fuel. To me it sounds ALOT like an o2 problem

Here comes the questions:

My mechanic buddy said I should try an OEM o2 (240 bucks ...uh no) because the standard 20 dollar o2 is probably not handling it right. Is there a real difference between splicing that o2?

Does anyone have any suggestions ?
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Old 11-25-2006, 03:47 PM   #3
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Hah, no.. I sold off my NA headers and I got a guy coming to pick up my IS300 bumpers in order to fund my AEM WB kit
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Old 11-25-2006, 03:52 PM   #4
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I WISH I got 15mpg. Lucky sob.
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Old 11-25-2006, 03:52 PM   #5
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i get similar mpg, i don't know what it is either. i don't think it's the o2 sensor since my a/f gauge sweeps back and forth during idle and cruise.
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Old 11-25-2006, 03:58 PM   #6
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definatly 02 and the afm might need to be tightened as well.
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Old 11-25-2006, 03:58 PM   #7
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I have no AFM :( Its MAP - HKS VPC
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Old 11-25-2006, 04:04 PM   #8
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well trim the curve on midrange for that kinda mileage you are dumping fuel somewhere leaning it out will bring you more hp as well
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Old 11-25-2006, 04:21 PM   #9
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your o2 wire could have been fried by turbo heat but hell andy runs with no 02 and still gets 22-23 mpg so trim back fuel and see if that helps other than that i dunno look for leaks under the car or something
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Old 11-25-2006, 05:48 PM   #10
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i just filled up. 175 miles, took 9.43 gallons = 18.55mpg, a little better but not much. I'm thinking it might be my maf, but wouldn't make sense in your case. It's also been recommended to my by olderguy to check you thermosensor in the back of the motor which can cause your car to think it's always cold and enrichening the mix.
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Old 11-25-2006, 06:18 PM   #11
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Quote:
Originally Posted by magnamx-5 View Post
your o2 wire could have been fried by turbo heat but hell andy runs with no 02 and still gets 22-23 mpg so trim back fuel and see if that helps other than that i dunno look for leaks under the car or something
Yeah I was gonna say....I dont even run an o2 sensor. And I still manage to get about 19-23mpg depending on how much I keep my foot in it while driving. I average 19-20 and thats getting into boost 5% of the time, or making a couple 2-3-4 gear runs for ***** and giggles.
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Old 11-25-2006, 11:05 PM   #12
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I wonder if the VPC can't lean up the idle enough on the 305s. Once you get the WB we'll easily be able to figure out what it can/can't do. But I'm averaging 25-27mpg with my 305s.
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Old 11-26-2006, 02:29 AM   #13
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Sounds like you need to get a wideband and do some tuning.
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Old 11-26-2006, 03:50 AM   #14
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im getting 21mpg and thats just a intercooled greddy! This thread is making me think if my setup is off.
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Old 11-26-2006, 11:07 AM   #15
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i get into boost more than 5% of the time but i dont use the brakes as much as he does living in the city. still get 25 average and 29 when i am good
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Old 11-26-2006, 05:07 PM   #16
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i dont have an answer, but instead of downshifting, just roll in neutral (up to a stop light or around a bend)
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Old 11-27-2006, 01:01 PM   #17
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Quote:
Originally Posted by Mach929 View Post
i just filled up. 175 miles, took 9.43 gallons = 18.55mpg, a little better but not much. I'm thinking it might be my maf, but wouldn't make sense in your case. It's also been recommended to my by olderguy to check you thermosensor in the back of the motor which can cause your car to think it's always cold and enrichening the mix.
Mach.. if I remember correctly we are both running the same cheapo bosch o2
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Old 11-27-2006, 08:01 PM   #18
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i'm actually running the original mazda sensor
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