Bad Gas Mileage!! HELP

ib_604

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Hey guys,

i know, i know, your laughing, bad gas mileage in a cobra? with record high gas prices? lol

but seriously....

My car was in storage, for about 6 months. I did a few things:
-changed out spark plugs to NGK Iridium's
-changed badly plugged fuel filter
-cleaned intake filter
-installed fuel PSI guage

before i stored the car i was getting about 350-380KMS/215-240MILES per tank.

I got the car back on the road....the first tank only lasted about 220KMS/135MILES

thought maybe it was bad gas, so i got some Gunk injector cleaner, and a fresh tank, and still was getting shit mileage...

My fuel PSI is usually between 30-40...

My QUESTION, (after searching) is, what could be causing this?

I am thinking a few different things, but i am not very knowledgeable...

1-need a re-tune because if the new fuel filter, maybe its working too well?

2-o2 sensors need to be cleaned?

3-new spark plugs gapped wrong? (i went with the norm off the forum, i think .037)


PLEASE give me your ideas!! This is annoying as hell....THANK YOU!
 

mike302

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Did you put the fuel filter in backwards?

can that cause bad gas milage, what else could it cause because one day I had a last minute plan to go to the track and it was like 8PM and I took my car in to pep boys to have them change my fuel filter and may be they put my fuel filter on wrong:shrug: I have bad (real bad gas millage)I waste about $90-$100+ on gas a week depending how much I drive:shrug:
 

ib_604

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no idea if the fuel filter was incorrectly installed, i wasn't there when my guy did it...he is a Ford Tech, so i am assuming he knew what he was doing....hopefully...

i was hoping that a re-tune would be the last resort....
 

69gt4speed

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Maybe u oiled down the maf sensor when u cleaned the air filter if u are using a k&n or equal. Need to get a handheld and look at closed loop a/f ratio should be ~ 14.7/1, switching back and forth fairly regular. Look at fuel rail pressure also. I'm using trix7's at .028 got 25 mph over the weekend cruising at 70 ish using bp 93. Wot different story.
 

ib_604

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thx for the replies!

i cleaned/lubed the filter, while it was off the car...

i have a diablo predator...not sure if i can check A/F on it? not too well versed in this stuff.
 

ib_604

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performance mods:

2.93 pulley
3.73 FRPP Gears
Mac CAI, stock MAF...90?
NGK TR-6 plugs w/ a .036 gap
MRT catted H-pipe
MagnaFlow exhaust
LFP dual pass H/E
Optima yellow top battery
Predator Tune
 

xenodragon

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thx for the replies!

i cleaned/lubed the filter, while it was off the car...

i have a diablo predator...not sure if i can check A/F on it? not too well versed in this stuff.


You can,

I just did it on my Diablo...you cant check the A/F per say but you can check
the closed loop (i.e. while its sitting at idle, or out of boost i believe). My tuner helped me do this

Hook the diablo up start the car and go to diagnostics, gas fuel, then scroll through the list of options and pick which things you want to track...i think MAF was one, and some other things that said Fuel, hit esc twice after you select what you want to track, log the data hold the RPMS at like 1500 - 2000 and look at the results

I couldnt tell you what any of the results mean but thats how you can view them
 

LuDamiKE81

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I got about 180 to a tank with about 70% hwy driving. If i stay in the city i get around 150. If i do a few pulls say 5, 2-4th runs (asshats like to go from rolls around here) ehh135 or so. Thats with jlt fenderwell cai,2.8/4lb,sra 3.73s, no cats with bassani's and turndowns. It made 450rwhp/500rwtq.
 

About2bite

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If you put too much oil on the filter it can get on the MAF and have an effect on the air/fuel
 

Jimmysidecarr

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Go to the parts store and buy some MAF cleaner.
Clean your MAF.

Let us know if that helped.:beer:

Too much oil or oil not quite dry(tacky) yet will get on the MAF sensor wire and cause all kinds of problems.

A semi dirty oil/gauze air filter actually filters better than a spanking clean one. It flows a little less, but as much as these filters flow, it's not going to hurt to run a slightly dirty air filter. 4 RWHP?:shrug:
 

ib_604

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interesting...didnt even know there was such a thing as MAF cleaner...i will look into that.

the one thing that i haven't got is the diablo MAFia....everyone seems to have that. do you need that or a bigger MAF? i am running about 475rwhp or something...
 

About2bite

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It comes down to how much boost you are running. If you are running the stock pulleys then where you are gapping it is fine, i'm at 19#'s so I gap mine a little lower at .032
 

69gt4speed

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Theory and practice says run the max. gap you can without wot misfire. I run n2o also, so I have to run a .028 gap even with the ix plugs. If I could run more I would but blowing off hoses from a nitrous misfire is serious bs. It all depends on combustion pressures. More boost or n2o, less gap is needed for a fixed spark voltage. Stock boost .036 is fine imo. Find a friend around if needed to do the testing and cleaning it's pretty simple stuff really. You can even look at maf voltage and see before and after cleaning maf voltage w a predator.
 

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