Bad Gas Mileage

Marko

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I'm getting like 14 mpg. With no WOT throttle runs. Just cruising highway and city.

My mods are only 2.76 pulley, idlers, JLT Budget HP kit, tr6 plugs and a catback exhaust and a dyno tune from 7 years ago.

I switched my CAI from a K&N FIPK to the JLT. Could changing that give me worse gas mileage.

Now, I don't know for sure what my mpg was before the JLT but my I'm filling up alot more often. :(
 

Mook

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How old is the fuel filter? Thats worth changing. Have you been running your air alot lately? That could be giving it a bit worse... But not likely the kind of drop youre seeing.

I see 17 under city driving and around 20 highway. So something is definitely off on yours.
 

Mook

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Its always possible your tune can need a refresher.
 

Marko

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Thanks. I had my Ford dealer change the fuel filter 500 miles ago and I never run the A/C. I would like to get a retune.
 

serb82

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Do you have a wide band installed in your car? You could have thrown off your air fuel ratio by moving the maf sensor to a different spot or a different clock position in the tube. I know on my saleen when I took the maf out to clean it, I changed the position and made it run richer, turned it back a little bit and got back to where it was tuned at.
 

Marko

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I put the Maf sensor in the same location. 12 O clock. It was like that on the K&N before and after the tune.

My tr6 plugs only have 3300 miles on them I was thinking about changing them.
 

Marko

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No. I don't have a wideband.


Do I need a bung welded into my stock H-pipe for that or no ?
 

serb82

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Yeah you would need one welded or you can cheat and plug it into a rear o2 spot if you don't have cats but it's not 100% accurate but to just get an idea were the car is running at.
 

Marko

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Yeah you would need one welded or you can cheat and plug it into a rear o2 spot if you don't have cats but it's not 100% accurate but to just get an idea were the car is running at.
thanks. i wonder if one or both of my O2 sensors are taking a shit??


i'm getting no trouble codes. I even checked today with my Xcal 2.

Should I return my tune back to stock and drive it around carefully (no boost) to see if it will trigger a trouble code??
 

serb82

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I would try putting back your old cai kit and drive it for a week and see if anything changes,stock tune and that pulley I would trust never know when you might step on it, in my opinion I would get a wideband or retune, the rear o2 only read how the cat is doing, the front 02 are what actually adjust your af ratio. You might also have bad gas or has it been many tanks?
 

Marko

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I would try putting back your old cai kit and drive it for a week and see if anything changes,stock tune and that pulley I would trust never know when you might step on it, in my opinion I would get a wideband or retune, the rear o2 only read how the cat is doing, the front 02 are what actually adjust your af ratio. You might also have bad gas or has it been many tanks?
Thanks for the advice. Yes, it's been several tanks now since i've been checking my MPG....
 

Marko

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Yeah you would need one welded or you can cheat and plug it into a rear o2 spot if you don't have cats but it's not 100% accurate but to just get an idea were the car is running at.
Just wondering,

How does my car get tuned without the bung welded in? Like having the A/F adjusted correctly. I had it tuned by Sutton 7 years ago. I have the stock H pipe with cats..,.
 

Aron

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They clamp the wideband into the tailpipe
 

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