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Huge Gas Problem

1K views 44 replies 29 participants last post by  tparker 
#1 ·
Alright, it seems lately, a lot of people has been having gas crisis...but I got the worse of it all. My Zx3 has mild mods to it and lately, my gas mileage has been getting real bad. Used to be I get about 300 miles per full tank, then it went down to 250 with some mods. Then it went to 210 about two months ago...now for the past three weeks, I've only been getting 185 miles per full tank...what's up with that?

I've changed spark plugs, wires, filters and every possible element I can think of. What could it be...it's not a heavy foot also because my 350z gets better mileage than my Focus.
 
#2 ·
I can really use some info on this same subject...about 2 weeks ago i put a full exhaust(header,flex,cat-back) on my zx3 and ever since that my MPG sucks...and i dont have the Heavy foot syndrome, i shift everytime the little yellow up arrow light comes on.
 
#5 ·
Yeah I have had this problem too....I dont know, maybe they are doing something to the gas to make it burn faster so you have to buy more...I dunno.....I didnt even get 20 mpg last tank...under 200 miles on a tank
 
#6 ·
Ditto on the mpg loss. Added the shorty header, hi-flo cat, flex, and exhaust to a FC intake. I didn't really notice a change in the range, but switched to premium to settle the "lope" that developed at idle. The lope is gone, but the mileage has been steadily decreasing. I expected some "drop" with the tire swap and the different sizing, but it continues to go down. Any idea if the SCT chip would help with this?
 
#7 ·
your answer lay within
sorry Bur but i dont have Leadfootitis ...Spelling?? and yet my gas is getting sucked from my car...i still use regular gas...should i use Premium?
 
#8 ·
I have all the basics done to mine as seen in my sig. I roll with the cruise on. I put her in 5th gear as much as possible. Im lucky to hit 27or28 mpg. It sucks. For a 4-cyl I would think it would be a lil better. Especially with the exhaust and intake on it.
 
#10 ·
If I'm cruising, I can still get 30mpg... 4-2-1/flex/exhaust/intake/SCT. Something a lto of my friends don't understand is that just because you're in a high gear doesn't always mean better mpg..when you havta hold it to the floor in 5th because you're only going 35mph, you waste gas. Smooth driving and maintaining speed are the best ways I've found to maximize fuel economy.
 
#11 ·
the O2 sensors have A LOT to do with gas mileage. When you guys are replacing headers, etc...what happens to your O2 sensors? (dunno, cause I have an SVT)....do you use an eliminator? Or the same sensor? I would get a dyno and see what the A/F is and perhaps get a chip to lean things out.
 
#14 ·
I dont beat my car to bad but I do a lot of passing and do get on it once in a while and I am still getting 325 to a tank.
 
#19 ·
couple things could be the culprit
1.what kind of spark plugs did you buy
2.how long has it been since you've cleaned out the carbon in the manifold and on the valves.

I have to clean my car out about once every six months and it still have the stock cams. with aftermarket cams you may have to do it often or start putting the lucas fuelinjector cleaner in the tank every month.

3.o2 sensors
 
#20 ·
Put chevron techron in a full-tank of gas, drive the p*ss out of it for 10~15mins (longer is better), and see if it improves.

my car gets worse and worse mileage if i keep driving like an old man with those 2.5 mile commutes; the above method brings mileage back to normal. Maybe your car needs a beating once a while like mine does.
 
#22 ·
I don't drive like a madman too often, and I get 240 per tank with mixed driving. (my mods are in my sig)

I ran a race header for a while, and didn't replace my o2s afterward, so could that be something? I've got about 72k on it right now.
 
#23 ·
Get a can of valvoline synpower throttle body cleaner, take off the intake tube and unplug the maf. start the car and start tapping the sprayer into the throttle body for a couple of minutes. stop and let the car idle for about another 30 seconds. if you can take this time to clean the maf with a little electronics cleaner. let the maf dry and reinstall the tube and plug in the maf. pull off the battery cables for a few minutes to reset the computor. restart the car and let the computor find the idle(it'll probably bounce around for a little bit cause the computor has to relearn with a clean system)rev the motor up and hold it just under 3 grand untill the smoke stops coming out of the tail pipe. don't be afraid to let off the gas and press back down.
shut the hood and go drive the piss out of it on the highway. done.
 
#24 ·
Miles per tank is an irrelevant measurement; use your trip odometer reading divided by the gallons of fuel used to find a true MPG measurement. Just because your gas gauge says it's on "empty", doesn't mean it is.
 
#25 ·
Yea my car is sucking gas like crazy too...but I suffer from acute ironfotitis or whatever I saw earlier. Haha
 
#26 ·
Dood... don't try and tell me that with mods like these:

SeanHylandMotorsports longblock with stage 2 SHM cams and ported head; Injen CAI; Tsudo cat-back; Eibach sportlines; B&M short throw shifter; Diablo chip; Steeda 4-2-1 Header; Steeda Underdrive pulleys...
you don't have leadfootitis.

Here's your mission. Right now get in your car... take it to the gas station... fill it up till the pump stops itself. Stop right there. Get on the freeway/interstate/some highway you're not going to stop at all on, set the cruise control @ 60mph and don't touch it.

Tell me how many miles you get.

I betcha its more than you've seen in a long time.



Fact is. I'm lucky if I get 240 on a tank. Its because I have leadfootitis and I know it. But if I head on a long distance trip to say, Vegas, Phoenix, or San Fransisco... I can get well over 350 miles on the same tank.

How you may ask? I DON'T TOUCH THE GAS PEDAL ON THE TRIP! I don't hear my engine ROAR... I don't let the RPMs get above 3500 if at all possible.

Trust me. Its not your car... its your driving.
 
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