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

 

[MikesDSM]

wouldnt it say on the tank how many gallons it is?

 

[arffy]

Originally posted by boostdevil
oh yah another thing, there aint no way in hell that our dsms have a 16 gallon gas tank, i have filled my gas tank up before when it was almost completely empty and the most gas i could get out of it was around 13 gallons

How did ya know you were "almost completely empty" if it was by the gauge ya better guess again....

 

[pneumo]

I just finished swapping fuel pumps on my Talon and I got a good look at the fuel level. When I parked the car the low fuel light was on, but when I opened up the tank I could see that there was still 3 inches of fuel in the bottom. That's gotta be about 2 gallons at least. I think they set up the fuel gage that way so when you go around corners you won't run dry.

 

[boostdevil]

well i knew it was pretty much empty because it had lost all its power, like it was barelly running, but what do i know im just some dumb idiot that know nothing about cars and just thought i would buy a dsm just for the hell of it give me a break

 

[Jetblack]

would lowering fuel pressure via afpr help in obtaining better gas mileage?

 

[Red GST]

if your gettin poor fuel mileage first check other things example plugs,wires,o2,air filter those will all effect gas mileage

 

[Jetblack]

well basically it all started when I switched over to the MAFt-blow thru-vent to atmosphere-w/ DSM LINK SETUP. i THINK its tuned pretty good I was just wondering would fuel pressure or how does fuel pressure affect a cars system.

 

[Defiant]

How sucky is it? You should be around 20mpg, less if you play with the boost much.

 

[ColonelOdem]

Ok, I have been getting around 18-20 mpg, I have no upgrades except for the removed silencer from the maf sensor. Today, I put an APC breather filter on my PCV on the valve cover.... I am wondering if I did it backwards or what because today after wards, I bought a full tank of gas (93 oct., the only grade my baby gets), and around 32 miles I noticed that I used a 1/4 tank! that's like 8mpg!!! Details: I have a Haynes repair manual, and I did the pcv check. It works perfectly so I screwed the nipple back onto the valve cover. I put a breather filter on over the nipple. I wonder if I should have put it over the hose going back to the intake or If I did it right but I should just throw the filter away and say heck with it. Please help, gas is expensive!

 

[flytalon93]

I did mine a little different. I got a oil catch can and hook it up in between the PCV and the intake manifold. What did you do with nipple coming out of the manifold?

 

[ericismyname]

There are a bunch of reasons you could be getting bad gas mileage, as for the PCV valve thing, unless you have a catch can, i would just leave it alone for now.

 

[ColonelOdem]

would it work If I put a breather filter on the hose to the intake manifold too? or would that mess up my MAS calculations? I did notice a better boost sensitivity when I blocked the hose. I have seen the filter used on the PCV on "High Rev Tuners" on the speed channel.

 

[jmargelo]

I get 17-20mpg, but I have some modifications. I'm not sure what mileage a stock eclipse is supposed to get, but the way you drive is gunna be a huge influence. In other words, are you boosting the hell out of it all the time?

Also, you cant accurately judge fuel consumption from watching the gauge move 1/4 tank. You have to wait til its empty and fill it to see how much fuel you actually used.

 

[ColonelOdem]

'jmargelo' "I get 17-20mpg, but I have some modifications. I'm not sure what mileage a stock eclipse is supposed to get, but the way you drive is gunna be a huge influence. In other words, are you boosting the hell out of it all the time?"

Your car is right on the money for good gas mileage! I really baby my car. I just read that after you modify anything with the intake or exhaust, that you should disconnect the battery for about 15 minutes to reset your ecu. I did that this morning and started it up, it died on me twice in the driveway. where do you get the catch cans? is it just a small cylinder that hooks up to the valve and the hose on the other end, that way there is a space to catch the oil? I say that you got good gas mileage because the 1000 already answered questions page said 18-20 is good.

 

[ColonelOdem]

Forgive me if I am wrong, I didn't know right where to put this bit of information. but if you have read my thread, and have had same problem or want to try it, read this first. : http://www.hastingsfilter.com/engineer/tsb_index.html

go to TSB-94-2R Positive Crankcase Ventilation in list on page to read info on this important part. By the way, thanks for all the help, I will definately go with the catch can!

 

[racer]

ok now let me clear this furs.PCV vlave is the niple that conects ur valve cover to the intake manifold.The breater is the niple (on the left side f valvecover) that conects the valve cover with the IC pipe or intake pipe.
So by puting a breater filter there u do not eliminate ut PCV valve.Breater filter is good thing to have.Removing a PCV valve on N/A engine is a bad thing to do.Removing PCV valve and replaceing the whole PCV sistem with OIL CATCH CAN on TURBO cars is a good thing to do cuz u wont lose boost under high RPMs and ur crank will be geting more ventilation.DO RESURCH and you'll find a lot (just type PCV).
Ok but now back to the title of this treath.The PCV sistem has noting to do with ur gas milage,SO dont worry about this.
FOR gas milage check: O2 sensor,sparkplugs and wires,air filter,properly working MAF,Fuel presure and check IF u runing too rich.Maight be from bad injectors.Maybe cuz of bad termostat and car runing cold all the time.Check all that.GL

 

[IronnFisTT]

do you still have the stock o2 sensor in the car?? if so, thats probably the cause for your horrible gas mileage. Im getting roughly 23-25mpg. As for calculating mpg based on the first 1/4 tank, dont even waste your time, my first half tank drops with less than 100 miles on the clock.. the second half takes forever to go down.

-attia
94 Tsi AWD
98 Supra Turbo

 

[ColonelOdem]

Originally posted by IronnFisTT
do you still have the stock o2 sensor in the car?? if so, thats probably the cause for your horrible gas mileage.


Yes, still have the stock 02 sensor, others are soo expensive and can't find them on ebay... well I found the problem after all my talon and I have been through these past two-three days... this morning I turned on the engine and it went to about 2500 rpm and shut off. so, I unhooked my b-filter from the wrong place of course (stupid me put it on the valve and blocked the manifold hose) and hooked stock position back up. she purrs at 750 rpm idle speed (except that darn lifter ticking). so, I put the b-filter on the hose coming in from the air filter? then block off the outpost from said hose? ( I can't find a catch can so I'm stuck with little filter)

 

[racer]

DUDE u are talkin BS now.The PCV sistem doesnt have anyting to do with ur RPM or gas milage.PLZ READ what I said above IronnFisTT. GODActualy it could have big thing if u didnt plug the holes at IC pipe and intakemanifold.I do not even think that you can keep the car runing with out plugin the intake manifold hole (after removing pcv).

 

[IronnFisTT]

Originally posted by ColonelOdem
...so, I put the b-filter on the hose coming in from the air filter? then block off the outpost from said hose? ( I can't find a catch can so I'm stuck with little filter)

if i understand you right, it sounds like you have it backwards.. you wanted your breater filter off the valve cover and you should have blocked off the nipple at the intake pipe. With the way you got it setup, youre allowing unmetered air into the motor.

how many miles on your car? your profile shows you have a 90.. im guessing you have over 100k. im willing to bet the o2 sensor is responsible for your shitty gas mileage. a new o2 sensor is $80 i think. gas is expensive, the new sensor will pay for itself.

as racer said, if you think this pcv thing is responsible for your horrible gas mileage, think again.

-attia
94 Tsi AWD
98 Supra Turbo

 

[ColonelOdem]

OK, sorry, you're right about pcv system, I've had it fixed now... so it is most likely my 02 sensor. now, I can pick one up from a salvage yard? do you mean the actual sensor or the housing? and what are reccomendations on 02 system? should I go to a salvage yard and get an EVOIII sensor housing or get the 2nd G. housing and sensor? Acutally, my car has 85K on her ...oh, one more thing, should I go ahead and get a 2g manifold when I get the housing/sensor, how much would it be to port the manifold?

 

[IronnFisTT]

yes, you want a new o2 sensor.. no way in telling that a sensor from the boneyard is any good. Youll need an o2 sensor for a 1g, im not sure that the 2g sensor is compatible. As for an o2 sensor housing, you can put a different one on like you mentioned for added performance but its not necessary. Same goes for the manifold.

Oh, and good luck finding an EVOIII at your local boneyard. As for gains with the 2g manifold, o2 sensor housing and porting, do a search or check www.vfaq.com

-attia
94 Tsi AWD
98 Supra Turbo

 

[scuRRed whiTey]

I DIDNT READ THROUGH ALL THE POSTS BUT...

you do realize it is very very very cold out
zero degrees and below that

during the summer i get about 350 miles to the tank
during the winter i get about 170-200

you do realize that turbos love cold weather
why?

cold weather = dense air
dense air more fuel

boost and cold dense air = lots of fuel being used

 

[ColonelOdem]

wow, I didn't know about that site...that should help me with every thing, thanks all for info! and it is winter wich is good for my car's performance (once it's warmed up) but with all that x-tra umph of cool air, the roads suck...

 

[IronnFisTT]

winter gas is also another reason you get worse gas mileage in the winter. but going from 350 to 170 sounds a bit extreme. i was getting 300 and now its 260ish to the tank.

-attia
94 Tsi AWD
98 Supra Turbo