Ok im about sick of this. 2000 civic si motor with 45k miles.

Over the last 10 months my gas mileage has continue to drop. I used to be able to get 26 average not gettin in vtec a whole lot, and 20 mpg FLOORED EVERYWHERE.

Now, i get an average of 19mpg driving completly normal, hittin vtec only sometimes, (driving the same as when i used to get 26mpg).

2 tanks ago I got 17.65mpg! WTF! So i finally changed my o2 sensor. Now i STILL only got 19mpg.

I already replaced my cap, rotor, wires, plugs, seafoamed a long time ago.

What is goin on, and how do i get the average of 30mpg that most people see?

 

What ECU are you running?

 

ewww sounds nasty. check injectors, maybe look at fuel lines. good luck

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueIntegraBoy &raquo;</TD></TR><TR><TD CLASS="quote">What ECU are you running?</TD></TR></TABLE>

im gonna go out on a limb here and say he doesnt know, based solely on the fact that he said "2000 civic si motor" instead of simply saying usdm b16aX

 

thats sucks, i have been rocking the b18c, getting 29-30 babying it, and 26 beating the **** out of it

 

Weird. But then again your method of filling your tank and resetting the trip odometer isn't exactly scientific. Have you been doing the same driving routine throughout this process?

I'm in for the conclusion. 17 mpg on 93 octane hurts.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">im gonna go out on a limb here and say he doesnt know, based solely on the fact that he said "2000 civic si motor" instead of simply saying usdm b16aX</TD></TR></TABLE>

and whats wrong with that? saying "usdm b16aX" means you know your ****?

 

i drive a hx (d16y5) and rarely hit vtec-e and get like 25 mpg.

 

haha since uve been flooring it alot(sounds like it) go change your fuel filter and tune it up right...

 

Sounds like you've got a nasty fuel leak to me. My 93 Si (D16Z6) has 271k miles on it and even driving like a jackass I get 33mpg (on a bad tank). There's no reason your car should be pulling any less than about 27.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Archidictus &raquo;</TD></TR><TR><TD CLASS="quote">Sounds like you've got a nasty fuel leak to me. My 93 Si (D16Z6) has 271k miles on it and even driving like a jackass I get 33mpg (on a bad tank). There's no reason your car should be pulling any less than about 27.</TD></TR></TABLE> Right as usual. There's somethign seriously FUCKED up some place to get those numbers, it's not related to "stomping on it" or anything of the sort..not with the displacement you have... Change out the fuel filter...it's possible that it could be a gas leak like Archidictus said which would really make sense as your gas mpg is slowly deteriorating...

Either a clog or a leak or something..

You running any aftermarket **** that would affect ur fuel (any electronics?)

What's ur mods?

 

for gas prices and your fuel problem!]

 

"im gonna go out on a limb here and say he doesnt know, based solely on the fact that he said "2000 civic si motor" instead of simply saying usdm b16aX"

^ haha read his a/c thread and tell me he doesnt know what ecu hes running. And remember to grab a pen and pad and take some notes cuz youre gonna learn some ****.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">im gonna go out on a limb here and say he doesnt know, based solely on the fact that he said "2000 civic si motor" instead of simply saying usdm b16aX</TD></TR></TABLE>

Thats probably the stupidest assumption I have ever heard. Does it make you happier if i say b16a2?

My ecu is P30.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TorquelessB16 &raquo;</TD></TR><TR><TD CLASS="quote">Weird. But then again your method of filling your tank and resetting the trip odometer isn't exactly scientific. Have you been doing the same driving routine throughout this process?

I'm in for the conclusion. 17 mpg on 93 octane hurts. </TD></TR></TABLE>

I always fill my gas tank to the complete brim when checking mileage. To the point where some flows out back onto my foot. That way I know its starting at the same level at each tank. No room for error there.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote"> Right as usual. There's somethign seriously FUCKED up some place to get those numbers, it's not related to "stomping on it" or anything of the sort..not with the displacement you have... Change out the fuel filter...it's possible that it could be a gas leak like Archidictus said which would really make sense as your gas mpg is slowly deteriorating...

Either a clog or a leak or something..

You running any aftermarket **** that would affect ur fuel (any electronics?)

What's ur mods?</TD></TR></TABLE>

I also forgot to mention that I put a brand new fuel filter on about 10k miles ago.

I am basically stock. Got catback exhaust 2.25", shortram with autozone intake. Hmm thats it.

How do I check for fuel leaks. Would it come out as a liquid and be visible or evaporate too quickly to see. Let me know anything else I should do.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jadugartir &raquo;</TD></TR><TR><TD CLASS="quote">"im gonna go out on a limb here and say he doesnt know, based solely on the fact that he said "2000 civic si motor" instead of simply saying usdm b16aX"

^ haha read his a/c thread and tell me he doesnt know what ecu hes running. And remember to grab a pen and pad and take some notes cuz youre gonna learn some ****.</TD></TR></TABLE>

This guy knows his ****!

 

i take it you get affended easily, i wasnt saying you dont know your stuff. just by the description of the problem made me think you probably didnt know what ecu you where running, no affense intended.

by the way, gasoline is a LIQUID, and will be visible like any other liquid. it shouldnt evaporate very quickly unless its near something pretty hot where its leaking.

how is the car running (driveability wise) w/ mileage that low if it where mechanical it would be an obvious problem, so im gonna vote most likely a leak as well.

SORRY i affended you.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by schardbody &raquo;</TD></TR><TR><TD CLASS="quote">i take it you get affended easily, i wasnt saying you dont know your stuff. just by the description of the problem made me think you probably didnt know what ecu you where running, no affense intended.

by the way, gasoline is a LIQUID, and will be visible like any other liquid. it shouldnt evaporate very quickly unless its near something pretty hot where its leaking.

how is the car running (driveability wise) w/ mileage that low if it where mechanical it would be an obvious problem, so im gonna vote most likely a leak as well.

SORRY i affended you.</TD></TR></TABLE>

its "offend"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Archidictus &raquo;</TD></TR><TR><TD CLASS="quote">Sounds like you've got a nasty fuel leak to me. My 93 Si (D16Z6) has 271k miles on it and even driving like a jackass I get 33mpg (on a bad tank). There's no reason your car should be pulling any less than about 27.</TD></TR></TABLE>
&lt;3 93 Si's Even with 100k more than mine it's still pulling awesome mileage, Sweet.

 

I was getting 35-40 mpg before I blew my D15 up. Mostly freeway driving though.

 

Any modifications to the car?

Check the spark plugs and exhaust tip for signs of running rich. Some areas of the US have poor quality gasoline, others run a reformulated version with up to 10% ethanol (or more from what I've heard from some users.) This could result in not only the people behind you smelling french fries, but also a less efficiently running engine.

It could also potentially be a ripped or ruptured diaphram on the fuel pressure regulator, causing an influx of gasoline into the engine. Most of this would get barfed out the exhaust, but not before being absorbed into and saturating your catalytic converter causing it to prematurely fail if this type of situation persists for long enough. A bad cat could also cause skewed numbers from your oxygen sensor. Also, running a faulty, failing, or incorrect oxygen sensor could cause this.

Think of it this way... The oxygen sensor is the single most important part of the fuel system, since the engine uses this sensor to determine the engines current fuel requirements (al beit after the fact, and in conjunction with the MAP, TPS, etc...) A gunked up oxygen sensor (coated in carbon) will not read properly, causing the engine to run rich, which will coat the sensor in even more carbon...

Check the plugs, report back...

 

check your EGR system along with other tips above.

with the stricter emissions, if the EGR system is messed up, say hello to shitty mileage.


seen it happen a few times

 

maybe you have the AC running? ha and no the SI doesnt have an EGR system.

 

Air filter?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dELfONiK &raquo;</TD></TR><TR><TD CLASS="quote">Air filter?</TD></TR></TABLE>

The air filter would have to be a solid brick of **** with a few pinholes in it to drop a B16's gas mileage down to 17

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Archidictus &raquo;</TD></TR><TR><TD CLASS="quote">The air filter would have to be a solid brick of **** with a few pinholes in it to drop a B16's gas mileage down to 17 </TD></TR></TABLE>
Maybe that's a new modification we haven't heard of yet?

 

maybe that seafoam knocked out enough buildup in the motor to plug the cat... =P