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

 

[Bud92gsx]

New wires,plugs, fuel filter, pcv valve.Get K&n filter.Make sure brakes are not dragging, and e brake is not dragging.

Also take your foot of the gas.In town go 1-3rd.When going on highway go 1-2 5.Just very simple to keep milage up.

 

[sean44kyle55]

my talon is a turbo tsi awd i have replaced font o2 and plugs and wires also have a vaccum leak some were my vaccum sits at about 10 right now but i dont have tht heavy of a foot

right now with gas almost 4.00$/ gallon it takes about 40 to fill from E

 

[Ricardo18]

170 on a tank? Are you drinking that shit!? I understand you have AWD, but that alone wont bring your mileage down that much.

I drove 300 miles and still was at 3/4 tank LEFT. After a fill up, 100 miles usually brings it to the "Full" line.

This is just with changing driving habits and MAKING SURE ALL MAINTENANCE IS UP TO DATE! (please do this first as improper maintenance will leave your mileage in bad condition. Do you have congested traffic?

This is not stickied, but this should help:

http://www.dsmtuners.com/forums/hangout/428910-amazing-fuel-economy-my-420a-2.html

 

[sean44kyle55]

traffic inst bad here and i do alot of highway driving both o2 sensors are good have a air intake system. i just want to know if there is anything specific tht would make my mileage that crappy. probably going to change my fuel filter this week and see if that helps

 

[Ricardo18]

traffic inst bad here and i do alot of highway driving both o2 sensors are good have a air intake system. i just want to know if there is anything specific tht would make my mileage that crappy. probably going to change my fuel filter this week and see if that helps

Trust me when I say this, if your fuel filter was bad enough to mess up your fuel trim, I doubt your car would be drivable. You need to list ALL the issues with the car in one place.

List them ALL here, and then ONLY then, we can make a somewhat approximate guess as to what your problem is. As your original questions is, you floor the car through half the tank and drink the other half. If you don't do those, then post all the car problems that you are encountering. Read the link I posted, that can help you identify some issues.

 

[Tamatalon39]

my talon is a turbo tsi awd i have replaced font o2 and plugs and wires also have a vaccum leak some were my vaccum sits at about 10 right now but i dont have tht heavy of a foot

right now with gas almost 4.00$/ gallon it takes about 40 to fill from E

well it sounds like you have the same problem I have with my TSI (Improper fuel guage readings)
becuase you are saying it takes 40$ at almost 4$ a gallon to fill up from E the cars have 16 gallon tanks and you are only using up 10. still sounds like it could be better but not as bad as it appears

 

[sean44kyle55]

all the issues are

vaccum leak sits at about 10 in hg
2nd gear synchro is bad
rough idle, idle surge of about 200-300
also it misses at idle
not throwing any codes

also forgot to put that sometimes when its already warmed up like just went for a drive somewere come home and go to leave like 10 mins later still warmed up and it will idle at like 2000

 

[Ricardo18]

high idle is killing your mileage. Fix the vacuum leak and that will fix your problem. Time to start hunting. Have you done any work recently on the manifold? Check all the rubber hoses in the engine bay and see if you can find your leak. It might be too small to detect the hissing noise for an idle leak at 2krpms, but here are a few tips:

Remove the intake, exposing the throttle body, turn the car on at idle, and cover the mouth of the TB with your hand to seal it. Be careful, and prepared as it will suck pretty hard on your hand. If the car dies, then you have a leak that is in the butterfly plate. If it doesn't, the leak is further back. Check your egr valve and tube routing, brake booster cable for cracks and all that good stuff. Let me know how you make out...(no funny jokes )

 

[sean44kyle55]

it usually is hard to start if the upic pipe is disconected because its not sensing any of the air that is coming in

but i will try that thanks

 

[Sinister96]

i get from around 10-13 mpg cant figure out whats going on. got the car with bad mpg. change plugs, rims tires, have maft and 3" maf, translab shift kit, newer solenoids, used 93 octane, only use about 1\4-1\2 throttle at all times and do alot of highway travel, oh and just went to evo3 mani and small 16g. next steps? wires, fuel filter\pump, and getting cel for fuel trim bank one now which wasnt getting when first got car.

 

[Dabane]

My 2g is almost completely stock, with 105k and depending if I'm flooring it everywhere or shifting at 3k I get between 23 - 28 MPG. I always fill up with 93 octane though.

 

[this_tsi_8urV8]

Mine was pretty bad, about 250miles to the tank full, sometimes even less. I spent a lot of time tuning cruise f.t.'s and i'm not even at 1/4 of a tank used and I have about 70miles. That a lone is already a good increase over my previous fill ups. Perhaps a lot of cars are in a need of a good tune.
I know I can still squeeze out some mpgs, bc at times, my afs are on the lower side while part throttle driving.

 

[Rick_4g63]

I can't tell how much I get since I'm having problems with my gauge. Can any one help? It's a pain in the a** having to fill up every time the needle hits 1/4.

heres a link to the video to show and explain exactly what I mean. Is it a fuel pump or?

Eclipse GSX Dash - YouTube

 

[Sinister96]

It might be your sender. Have you replaced the pump lately? If so maybe the sender unit got messed up. If not could be bad. The sender unit is a potentiometer that send a voltage to turn on the light when reads low (long story short). If the unit is bad it could be reading low to early. It could also be a bad connector, check to make sure the connectors on the pump assembly are tight and not corroded. Spray them down with contact cleaner. Also try checking the voltage going to the unit. If the light goes off sometimes when you rev the engine, the unit might not being getting enough power to it. Electrical output of alternator goes up as revs go up, maybe when voltage goes up the sender has enough power to register a true reading.

 

[Rick_4g63]

It might be your sender. Have you replaced the pump lately? If so maybe the sender unit got messed up. If not could be bad. The sender unit is a potentiometer that send a voltage to turn on the light when reads low (long story short). If the unit is bad it could be reading low to early. It could also be a bad connector, check to make sure the connectors on the pump assembly are tight and not corroded. Spray them down with contact cleaner. Also try checking the voltage going to the unit. If the light goes off sometimes when you rev the engine, the unit might not being getting enough power to it. Electrical output of alternator goes up as revs go up, maybe when voltage goes up the sender has enough power to register a true reading.

I haven't replaced, nor swapped anything into or out of the car. I got it Nov. 2011 and all I've done was fix the oil pan since the idiots before me put silicone on the tube that goes to the oil pan, to "prevent" it from leaking, instead of putting a gasket and bolting it on. I don't know if it has a stock pump or if its aftermarket. I'll check the sender to see if it's that, since I don't want to replace the whole pump assembly yet. Can a bad alternator also cause this? Also, what about the gauge? any idea why it stays at 1/4?

and thank you for your response.

 

[MikeSD]

does the gauge ever go above 1/4 when you fill up?

it is most likely not the gauge, but the actual sending unit..or actually unit(s)
The hanger that has the fuel pump (passenger side) in it has a sending unit for the fuel level gauge.
The other side (drivers side) has the sending unit for the "low fuel level light"

for the fuel level it could be as simple as the clip at the hanger is not fully seated or the actual hanger is not lined up correctly. I know this because I had the same problem and a fellow member helped me out. There are little dots on the top of the hanger and they have to be lined up correctly for the unit to read correctly. You might want to look into that before ripping your dash apart.

 

[Leonthefaded]

I get around 150-170 a tank.

 

[Rick_4g63]

does the gauge ever go above 1/4 when you fill up?

it is most likely not the gauge, but the actual sending unit..or actually unit(s)
The hanger that has the fuel pump (passenger side) in it has a sending unit for the fuel level gauge.
The other side (drivers side) has the sending unit for the "low fuel level light"

for the fuel level it could be as simple as the clip at the hanger is not fully seated or the actual hanger is not lined up correctly. I know this because I had the same problem and a fellow member helped me out. There are little dots on the top of the hanger and they have to be lined up correctly for the unit to read correctly. You might want to look into that before ripping your dash apart.

Yeah it does go up, but it fluctuates; for instance if I fill up my tank, drive 30 miles, turn off the car for the night, and the next morning turn on the car, it'd be at the middle of 4/4 and 3/4. After a couple minutes the gauge would go back up. The problem is that the gauge stays at 1/4 and doesn't go any lower.


I didn't know that, thank you. I didn't want to be messing around with anything involving fuel if I wasn't educated enough. I was thinking it could be the whole fuel pump assembly. But, the hanger you speak of are underneath the back seats right?

once again I appreciate your help

 

[Sinister96]

on the awd models the fuel pump assembly is under the rear passenger seat. apparently on the drivers side is the sender for the dash gauge. If you pull up the back seat youll see to access plates thats were they are at. pull off the seat and check the connectors first. get some contact cleaner spray unplug, clean them first. then get an multi meter and check the input voltages. start with that easiest to do. report back and we can go from there.

 

[Jake1987]

I have the same problem. Just bought the car. When I was test driving it everything was good. Then over the weekend I was going 90mph on the freeway to see how much boost the dude set before me. It was 15psi. Too high considering its all stock except an hks bov and megan racing exhaust with straight pipe, no cat. then after that the check engine light went on. So yesterday i drove home from work which is only 5 miles away and i lost 1/4 tank. Im afraid to drive it until i got the problem resolved. 1/4 tank in only 5 miles freaked me out.

 

[BoostKrazy]

I have a 97 NT gs, I drive this car like 100 miles a day minimum, the other day I sprayed throttle body cleaner in the throttle body, it started blowing white smoke out the tail pipe, started idling rough, check engine light flew on, says car is running lean, but my MPG went down by 1/2, I used to fill up once a week, now I have to fill up twice... This sucks, might as well start taking the gsx to work when it's up and running

 

[eclipsemodder]

Hey guys got a 99 GSX and I'm only gettin bout 120 miles on a full tank !!!
Help. Any suggestions would be greatly appreciated thank you.

 

[96' Eclipse GS]

Any Emission Codes that you know of? You don't have much on Bolt-on's, so I start with checking a few different areas?! Start any noticeable fuel leaks, FPR, fuel injectors dumping like crazy, that might sound dumb, but you never know, right?

 

[Jake1987]

I had the same problem and i was running a straight pipe. I put the cat back on yesterday and the problem seemed to go away for now. Change your o2 sensor if you havent yet.

 

[nek]

Its the 02 sensor no doubt. Onlything that messes up your mileage that bad beside a hole in your fuel tank.