i have a 94 civic hatch cx. with 188k milage. i'm getting horible gas milage, i first thought the car has a 12gal. tank, but cars.com says it has 10gal. tank, and autotrader.com says it has 12gal. so what does it really have??? but i'm only getting 200 miles to a tank. (only 8gal used, cuz at 2gal left, my gas needle is at red empty) even if i use the full 10 or 12 gal i'm only getting 250 miles to a tank, thats still not even near 30mpg. and the car is esitmated at 40+ mpg. the car is bone stock, i've tried cleaning my injectors, all tires are inflated properly and same size. my idle control is turn up all the way to prevent the car from dying out because it does have a idle problem(goes up and down) so that could be the problem but didn't think it can effect it so much. also stock tranny and i dont have a gauge, can someone tell me at what speed do i shift at to get the best gas milage. i dont shift high at all, i shift at 15, 25,35,40. and getting these mpg. any help would be great. thanks.

 

200 miles for 8 gallons is 25 mpg which sould good to me
i only get about 180 mile for 10 gallons in my built lsvtec 18-20 mpg

 

I get around 30mpg in my Close to stock b16, its in a Stock Cx hatch, and I have a heavy foot.

 

my y8 w/ exhaust and k&n air filter i got about 38-40 depending on how i drove...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">i have a 94 civic hatch cx. with 188k milage. i'm getting horible gas milage, i first thought the car has a 12gal. tank, but cars.com says it has 10gal. tank, and autotrader.com says it has 12gal. so what does it really have??? but i'm only getting 200 miles to a tank. (only 8gal used, cuz at 2gal left, my gas needle is at red empty) even if i use the full 10 or 12 gal i'm only getting 250 miles to a tank, thats still not even near 30mpg. and the car is esitmated at 40+ mpg. the car is bone stock, i've tried cleaning my injectors, all tires are inflated properly and same size. my idle control is turn up all the way to prevent the car from dying out because it does have a idle problem(goes up and down) so that could be the problem but didn't think it can effect it so much. also stock tranny and i dont have a gauge, can someone tell me at what speed do i shift at to get the best gas milage. i dont shift high at all, i shift at 15, 25,35,40. and getting these mpg. any help would be great. thanks.</TD></TR></TABLE>

FIRST you need to:

run SEAFOAM in your tank / intake / oil

1/4 intake 1/4 oil DO A SEARCH

Then..
change the fuel filter
new pcv valve
wires
plugs
dizzy cap
dizzy rotor

maybe new air
that should fix you up. Worked for me. My 94 was getting 30mpg, after all those changes I was getting 40

 

also, to get 40 in my cx you have to drive like a bitch.

ie; gas easy, shift sooner, etc... granny

 

the idle sounds like the IAC on the back of the intake manifold mine was doing that and the screen inside of it was built up with carbon, i cleaned it out and it idled nice, does the ecu throw any codes? and if not just check the 02 sensors for resistance just for ***** and giggles

 

1. Fuel filters have NOTHING to do with poor gas mileage. Please explain to me how a restriction in fuel delivery translates into too much fuel getting to the engine.
2. Fix the idle surge problem and set your base idle properly. The two common problems are IAC and FITV. The FITV is a donut with a thimble in the middle that bleeds air during warmup. Sometimes the donut gets loose and can be screwed back down so that it seats properly. The IAC needs to be removed and cleaned with a methylene chloride based brake cleaner or choke cleaner. With the engine warmed up, remove the connector from the IAC and set the base idle to between 500 and 600 RPM, replace the connector and clear your code. Idle should stabalize at 750. If idle is still not stable, you have a vacuum leak somewhere.
3. I agree that if you have not replaced the plugs, wires, rotor, and cap with quality parts recently, you need to do so.

 

i say it may have to do with surging idle as well.

this guy already seafoamed i believe, he did posted about it before.

i have a stock lx just did my mileage yesterday 9.7 gallons went 350 miles even, thats with a mix of hard driving, grandma driving, and super slow moving traffic.


i believe amckee has given you best ideas here, as far as idle, mine goes between 700 - 900 depending on what extra utilities im using, wipers, lights, brakes, stuff like that

 

Might wanna see if you can get another set of injectors somewhere and try those. I had a 90 CRX HF that was supposed to get 50+ MPG and I was getting 22. Ran good smooth all that never did figure it out but somebody suggested that I should have pulled the injectors and try another set or have them sent out to RC to be cleaned and checked.

 

where can i find and check my FITV?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">where can i find and check my FITV?</TD></TR></TABLE>

it's attached to the bottom side of your throttle body.

I was testing my IACV today, and once I removed the connector the car shut itself off. I don't know if this is normal.

 

I get between 31 and 35 in my 260,000 miles bone stock D16Z6 Civic Si (1993). I have a K&N filter and an MSD SCI with external coil and cap to help that figure.

The tune up (cap, rotor, wires, plugs) isn't a bad idea and should help you quite a bit, but that idle problem (FITV or IACV) is going to screw you up, especially if you've done something stupid like turning the idle screw all the way up to mask rather than fix the problem .

Come on now; if you can't drive like a real person and get 33+ in that car - and the tank size doesn't matter, now does it - turning an idle screw isn't going to help you at all.

 

its not too much of a problem. The D15B(jdm) in my civic hatch cx gets about 250 at 10 gallons and 300 at the 350 at the most in highways. but before the tune up it only got 190 miles at the most which was crazy amount of wasted gas. After tuning car ran faster and burned less fuel. Its all about the proper air/fuel mixture. It could be from a clogged cat, to throttle body settings to ECU to whatever. My suggestion is to take it to a shop that does "real" tune ups and have them check it out. It might cost some cash but you'll end up saving in gas money. Hey at least gas prices went down, a arco down the street from my house is at $2.70/gallon

 

ok so what do i do to my FITV once i've taken it out?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lv6l &raquo;</TD></TR><TR><TD CLASS="quote">ok so what do i do to my FITV once i've taken it out?</TD></TR></TABLE>

replace it

 

Ok, it's miles per gallon, not miles per tank. So search around to one of the many posts that tell you how to calculate it correctly first. Dividing the max tank volume by your odometer reading is way off and not even consistant.

Running rich or lean causes poor gas mileage, so a restriction in the fuel delivery system could in fact cause poor mileage.

Test the O2 sensor for laziness. Make sure your brakes, especially ebrake aren't dragging. How's your alignment?

 

alignment is good. car will drive striaght for over 15 sec. but my steering wheel is turn to the left when going striaght, car still goes straight and smooth, doesn't turn to any side at all. dont know if that is consider good alignment. my calculation is about my tank, 200miles to a tank, devide that to how many gal i've used will give me the miles per gal. i came up with 20mpg. i have tried seafoaming my car. works, i've notice more power but gas wise, didn't do much. i also used lucas fuel injection cleaner, i've used this on many of my other cars before, all of them gain at least 50 extra mile to a tank but for my hatch, didn't do nothing. i've tried cleaning my IAC and the gay idle still there, so i'll try replacing my FITV and see if i can lower my idle ****. does anyone know how much a FITV would cost???

 

Don't replace it yet. If thats the problem, I told you how to fix it in a previos post.

2. Fix the idle surge problem and set your base idle properly. The two common problems are IAC and FITV. The FITV is a donut with a thimble in the middle that bleeds air during warmup. Sometimes the donut gets loose and can be screwed back down so that it seats properly. The IAC needs to be removed and cleaned with a methylene chloride based brake cleaner or choke cleaner. With the engine warmed up, remove the connector from the IAC and set the base idle to between 500 and 600 RPM, replace the connector and clear your code. Idle should stabalize at 750. If idle is still not stable, you have a vacuum leak somewhere.

 

oh, thats pretty helpful i'll give it a try. umm i took off my IAC before and clean it very well with carb cleaner...is that a bad thing? can i still use brake cleaner to clean it again?

 

Either will be fine though, if you use brake cleaner, you want to use one that is methylene chloride based like Gumout.

 

The only accurate method for measuring MPG (miles per gallon) is as follows.

1. Fill the tank, reset the trip meter.
2.Drive it till at least half the tank is empty (on the gauge).
3. Fill the tank again, record the mileage and gallons used.
4. Divide the miles driven by the gallons used = MPG

Got it!

 

i get around 300 miles when it gets to the E in my stock CX. BONE STOCK. its a lot better than my old 94 accord ex that got prolly 20mpg on freeway,

 

i open up my throttle body and look under it to find my FITV. i still can't find it. i have a 94 cx hatch. can anyone help? pictures would be great if availble.