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1999 OBS black pearl (suki)
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Discussion Starter #1
My 1999 OBS 5mt Is only getting about 23 highway & 17 or less city mpg, even with ginger driving. The plugs are ngk iridium gapped to .43. Wires are ngk. The fuel filter has less than 5 k on it, I did replace the front O2 sensor with a Bosch unit. I've heard that these cars can be rather picky about those... But, I'm wondering if my maf sensor isn't bad as well. How could I tell if any of those are my issue? I've got an obdII scanner, so if anyone has the O2 sensor voltage parameters, that might be usefull. I apologize for my grammar, spelling & sentence structure, it's late. Thanks in advance.
 

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00'RS/02' WRX stgEleventy
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Where do you live?

Winter gas in the north always drops mileage some..

Every year the same flood of "whats wrong with my mileage"..

Sent from an other planet (Tapatalk)
 

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The subaru of many acronyms
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yep theres a mixture of i believe more butane which drops mpgs a bit, that compined with snow tires which have more rolling resistance can drop your mpgs a good bit.

if you want to clean your maf, CNC makes a good maf cleaer, pull that thing out and apart and spray the crap out of it with the cleaner then let it air dry, dont try and rub it with a qtip or anything.

if your still curious obut the o2, does your scanner read in voltage or lambda? i use my laptop with ecuexplorer (free) and a $7 ebay vagcom to read all the parameters, including the narrowband o2 which can be displayed in A/F or Lambda.
 

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1999 OBS black pearl (suki)
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111 Posts
Discussion Starter #4
It displays in volts & that would make sense, around October - November, my mpg's took the dive.
 

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00'RS/02' WRX stgEleventy
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Check the PCV or any vaccuum line, they get clogged with oil rather quickly on the 'brus.
This.. and any other maintenance items that should have been done and haven't.. fuel filter maybe...(not saying its part of the problem, but at 14yrs old it might need one to be happy)

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1999 OBS black pearl (suki)
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111 Posts
Discussion Starter #7
In the last 5-7K, I've done the pcv, fuel filter, both air filters, & I've seafoamed it a couple times. However, I have been meaning to clean the tb & iacv. I'm trying to think of other maintenance items I've done, but my memory is a bit hazy at times.
 

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'MURRICA!
Hybrid Camry
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5,700 Posts
Another thing: Check your speedo with your phone's GPS.

I know mine is way off depending on what set of tires I'm rocking. (as much as 12% off) which can mean an additional 2mpg that you're not "seeing".

Also, if you're rolling on heavy rims and tires that'll drop your MPG's.
 
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