Bad Gas Mileage [Merged 9-6]

[99GST]

I am still getting some pretty bad gas mileage.

I am only getting about 19.7 mpg with mostly city driving shifting at 4k.
I have already replaced my front O2 sensor and am looking to replace the fuel filter.

I have a 99gst with about 55k miles on it. Should my fuel filter already be bad?

What else should I check or change? I have NKG plugs and Accel wires are on the way.

Thanks,
Nathan

 

[Mike1992]

Well, my 300-350 miles max is mostly if not all city driving, if it were all mostly highway driving i bet its get about 400

 

[Defiant]

just switched from 87 octane getting 400km's to 89 octane getting about 500km's and running smoother with more power.

You're hypnotizing yourself. Higher octane has less energy in it, and will give less mileage- but not enough that you'd ever see. It also leaves more deposits. On an N/T, you should run the cheapest gas you can find. It has no use for more octane.

 

[Slipstream]

My tank reads empty at 200 miles...without fail, but the 1/4 tank left in it before the light actually comes on gives me another 100 miles...so 300 miles... but that's running on fumes.

 

[dsm4life]

My warning light likes to come on at a hundred miles into a tank, just for laughs. Then it goes off again and waits for 250.

haha mine does the same thing

 

[FourG63GST]

I get 160 miles per tank. You = Stop whining.

 

[Your_Dead]

atleast some of you have working gas gauges. i bought mine and drove it the full hundred or so miles ot my house and was like wow it still has half a tank. then drove it another hundred and said wow still half a tank. then the gas light came on and well ill be damned. the gauges reads fine from full till just less then half a tank it just stops. any ideas on this one(sorry for thread theft). i have no clue but yeah i get about 250ish per tank

 

[doobie1121]

160 miles on a tank of gas!!! that blows i hope its not a daily driver. By the way im not whining about my MPG i just wanted to know why the sudden drop so maybe i could fix it.

 

[FourG63GST]

I'm getting horrible gas milage since I got this car. About 160 miles for a full tank.

I have K&N, Vr4 pump rewired, New fuel filter, new ECU caps. Cant figure out what is wrong and why its gulping down my gas.

Any ideas on what to check? Could it be a bad MAS? Or a bad ECU? Or Bad Injectors?

I put in new NGK's plugs about 4000 miles ago.

 

[leakyfaucet]

How old is your oxygen sensor?
Also, that rewired VR4 pump might be overrunning your stock fuel pressure regulator, causing you to run rich.

 

[FourG63GST]

Ive got the bad gas milage since even b4 the fuel pump.

Its a brand new denso o2 sensor.

 

[FourG63GST]

I know Im just playing. And yeah, its a daily driver. Sucsk eh?

 

[Twizzle]

150 vented - ~300 blow thru

 

[Tandiey]

Hey guys,
I have a 91 Eclipse GS-T... After about 30 minutes or so of driving, my car will start to buck badly on WOT. As I keep driving normally, it will get worse and worse until I can't hit the gas pedal more than 1/4 of the way at all. It is really bad on hills and if I keep driving it, it will get so bad you can't use the gas at all. It literally will not move. Does anyone know what in the heck it is? I have changed the plugs and gapped them accordingly, but it didn't fix the problem. People have said that it could be everything from my wastegate, to intake hoses, to bov. I am going to test it for leaks today, but I hardly think that could cause a problem even when not boosting. If anyone knows that'd be awesome!!! Thanks...

 

[nurseryboy]

Hey man,

Sorry, I was away on vacation so I didn't have a chance to post. I got my car back as soon as I got back from the vacation, and it was all fixed. The problem? A piece of rubber that connects the uicp pipe to the intercooler had started to come apart. I guess the amount of air it was letting out caused all the problems. The shop fabricated up a new one for a few bucks, and since then I have driven it 2 days and over 300 miles, and it is running great. I think it actually pulls more than it did a few months ago (maybe because it was leaking some back then too?). After my expirence, I wouldn't be suprised at all if you have a leak. It is amazing what a little one can do (read the beginning of this thread).
Hope that helps.

 

[97GSXAUTOX]

I get the worst gas mileage in the world now-and i don't know why and can't afford it and might have to sell th ecar if it isn't fixed-cause its way too expensive-I have done just the normal mods-new BOV-intake-exhaust-and little other things but i can't ride in my car for more than an 1hr and a half before i have to fill up again-and premium is't cheap-why did it get so bad???

 

[97GSXAUTOX]

sry for double post- my exhaust is black-the smoke is like thick black-is it possible the o2 sensor is broken making me run realy rich? thanks so much

 

[blitz43]

it my be the o2 sensor before the cat ....or
is the bov vented to the atmosphere??? cause i heard that with bov vented the comp would dump too much fuel into the engine casuing it to burn more fuel...

or it could be that ure motor is flooded.

you checked ure spark plugs to see what shape they are in?

 

[97GSXAUTOX]

yeah-i don't think i get what you mean by atmosphere-it does not run back into the intake-it is an apexi twin chamber BOV with 4 holes for pressure release but could that realy be it-i hope its the o2 sensor-are those cheap to replace

 

[Defiant]

This is going to be another one of those stories, isn't it?

Okay, 'fess up. Tell us all of the modifications on your car, since your profile page is blank.

Also, tell us specifically how many miles per [/b]gallon[/b] you're getting.

Step One: get a 1G BOV, and route it back through the intake. Yes, you may have to try and exist without a cool PSSSssss sound.

 

[mitsuclipsegsx]

i know this has been covered many times, but i gotta ask anyways i am getting 16mpg and all ihave is an intake,type s bov and ic pipes and the 3" exhaust,1gtb and boost controller isnt even in yet i'll probaly be getting like 12mpg, my plugs and wires r brand new accel and ngk, no boost leaks the only thinhg i could think is i only drive 10 min to work, any suggestions, maybe new fuel pump??

 

[herostar]

your O2 sensors could be going bad. Mine were, and before the check engine light came on I was getting about 12mpg.

 

[mitsuclipsegsx]

haha i can't belive i forgot to metion that, i just replaced the front o2 sensor didnt do jack shit, maybe the one next to cat but i am not gonna waste another 100 like i did w/ the front one

 

[herostar]

did you check the compression in your cylinders? Does the car feel slow? Maybe you're just driving really hard... I can get almost 30mpg on the highway, but driving very hard at all it's about 17mpg...

 

[DSMeclipse4G63]

the rear o2 wont affect gas mileage...

 

[14.5 drift]

did you check the compression in your cylinders? Does the car feel slow? Maybe you're just driving really hard... I can get almost 30mpg on the highway, but driving very hard at all it's about 17mpg...

your telling me with a 60-1 and a stroker you get 17mpg driving hard? I am bone stock (boost controller is all) and I am lucky to get 14 mpg when I drive hard.