im wondering what could be the possible cause of bad gas mileage on my 91 si. i thought the car is supposed to get really good mileage (like 30-40+mpg?) but mine seems to be getting around half of that for whatever reason. any ideas? the only engine mods are intake and aftermarket cat, though i dont really consider that a mod. the engine pulls strong and the car runs really well otherwise.

 

Is this city or highway? You should be getting anywhere from 20-30 mpg with a mix. Maybe it needs a tune up? How many miles on the motor? How heavy is your right foot ?

 

yeah i was having very bad milage and still dont know weaters good or not,

i wish i get some where above 30 miles per galon,

how to tune up,?

 

my dpfi crx dx 1990 gets 31 mpg city and i dont know highway. i know i get 289/tank in city

 

sorry guys, i should have clarifed this is strictly city driving, 137k on the engine, maintained extremely well by the previous owner, and i baby the car. however, i do quite a few short 5-10min trips throughout the day in the car, i thought that might have something to do with it. i was considering just doing a tune up anyway to see if that makes a difference but was wondering if it could be something else.

 

ya know i was thinkin about how ive had a couple different civics, some got good mileage some didnt. what if the speedometer is off? they are old cars and if the speedometer is reading too slow it would effect your odometer reading wich would effect your mpg calculations, why dont you check on yahoo or somethin and try to see if your odometer reads correctly?

long shot?

 

my b16 has been getting better and better gas milage.

first time i got 150 miles. second time i got 250. 3rd i got 300. And all this time i only filled it up with 9.5-10 gallons.

our tanks are 11.9 gallons. im going to go for 330. and see how much it will take

my only worry is that for some weird reason it will only let me put 9.5 but at the same time be using more then the amount i can p ut in it....

oh well. we'll see soon enough. im just getting into the red on the gauge with 270 miles. .. 60 more to go!

 

I drive an 88 CRX DX Automatic and so far have had about a 43MPG average. I have to admit I drive sort of like an old man but I don't mind at all when I get high MPG.

I plan to do an auto to manual swap as well as MPFI but that will all come in time. If you guys are interested in it check out GasSavers.org. Great site, lots of good info and a great bunch of guys as well.

I dunno what the hell the problem could be with such low MPG though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by easynowrudeboy &raquo;</TD></TR><TR><TD CLASS="quote">however, i do quite a few short 5-10min trips throughout the day in the car, i thought that might have something to do with it. </TD></TR></TABLE>

You would be absolutely correct in thinking that this has something to do with it. Your car probably takes around 5-6 miles to warm up. Since your car is never warmed up properly:

1) The o2 sensor doesn't work right (not enough heat)
2) engine runs richer (high temps = leaner AFR)
3) Higher RPMs due to the FITV.

Short trips will absolutely kill your fuel economy. If it's at all possible, install an engine block heater and warm up your engine 30 minutes before each trip.

 

Bingo!

That is the only thing I hate about living around 6 miles from work. By the time I'm pulling in the parking lot it's just getting to normal temp.

If I drive freeway I get 30+ and on short trips To work and store I get about 20.

If you haven't changed your O2 sensor yet, it might get you a couple mpg's back.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">Bingo!

That is the only thing I hate about living around 6 miles from work. By the time I'm pulling in the parking lot it's just getting to normal temp.

If I drive freeway I get 30+ and on short trips To work and store I get about 20.

If you haven't changed your O2 sensor yet, it might get you a couple mpg's back.</TD></TR></TABLE>

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

You would be absolutely correct in thinking that this has something to do with it. Your car probably takes around 5-6 miles to warm up. Since your car is never warmed up properly:

1) The o2 sensor doesn't work right (not enough heat)
2) engine runs richer (high temps = leaner AFR)
3) Higher RPMs due to the FITV.

Short trips will absolutely kill your fuel economy. If it's at all possible, install an engine block heater and warm up your engine 30 minutes before each trip.</TD></TR></TABLE>

ok thanks guys, thats what i was thinking. i noticed that the car never does fully warm up before i actually finish my 5 minute trip, so i figured my mpg might be suffering alot b/c of that.

 

how do u know if your car runs rich? and how to solve?

 

I've also had the same problem lately, I have 146k on my 91 Civic DX Hatch auto. I used to get 400miles on highway when filled but lately only getting around 170 for half... so who knows.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dynamitezz &raquo;</TD></TR><TR><TD CLASS="quote">I've also had the same problem lately, I have 146k on my 91 Civic DX Hatch auto. I used to get 400miles on highway when filled but lately only getting around 170 for half... so who knows.</TD></TR></TABLE>

DUDE! THat's low. Even if it was just cold starts you should be getting around 250 miles.

Me thinks your oxygen sensor might be bad...

Time for a tuneup

 

my crx only got about 155 mi after i filled it up. about how much does the o2 censor cost and what do i say i just need and o2 censor?

 

Get an OEM one if you can ($$$) or a Bosch from an auto parts store, should be in the neighborhood of $30-$40.

 

does this make a difference after u put on?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dr@ke &raquo;</TD></TR><TR><TD CLASS="quote">does this make a difference after u put on?
</TD></TR></TABLE>

O2 sensors tell the car to dump more or dump less fuel so yes. the car is stuck in open loop so it will run rich until the car is warmed up. Also fuel filter and maybe leaking injectors can cause very poor fuel economy.

 

Hate to break it to you buddy but a new 1991 CRX Si was only EPA/CAFE rated for: 28 mpg city/33 mpg hwy and that was when the car was brand spanking new unmolested with aftermarket stuff and years of use.

Don't take my word for it, I'm not making this up.
http://www.fueleconomy.gov/feg/noframes/7473.shtml

EDITED TO ADD THIS BELOW:

Let me see if this works so you can see what all the <U>1991 </U>CRX trims were rated for:
Honda Civic CRX.....Trans..Gas......mpg.mpg
.......................................Type......c ity..hwy
4 cyl, 1.5 L, Auto.....(4 sp), Regular 29 34 &lt;------DX Auto
4 cyl, 1.5 L, Manual (5 sp), Regular 32 36 &lt;------DX Manual
4 cyl, 1.6 L, Manual (5 sp), Regular 28 33 &lt;------Si Manual
4 cyl, 1.5 L, Manual (5 sp), Regular 49 52 &lt;------HF Manual

That's why I got myself the HF! 50MPG is sweet!




Soon to swap out the 15's for these 13" VX wheels to help get more mpg!




Modified by 97SS at 4:50 PM 9/21/2006

 

the op said he was getting 15-20 mpg so i do see a problem. So what if the car is old so is yours and you said you get 50mpg, So your car which is 3 years older then his can get gas mileage equal to what it did 15 years ago and this guy can't. oh yea the 88 crx si should get better then the 91 si since there is about two hundred pound difference. Don't believe me FAQ.

 

Relax SFlCrx...the OP said, "im wondering what could be the possible cause of bad gas mileage on my 91 si."...where do you see him saying 1988 (which I do know the weight differences trust me that's why I was looking for a 1988/89 CRX HF becuase all 90/91 CRX's gained weight due to the door reinforcements and other weight add on).
Also he was incorrectly expecting to see "(like 30-40+mpg?)" so I just wanted to point to the data to show him what to realistically expect, and not knowing his mileage and quality of aftermarket components, that may seriously affect his mileage (besides the normal things, tune ups, tire pressure, tire size, added weight, aerodynamic mods, etc)
My CRX has low mileage and is completely dead stock (besides the wheels and coilovers, power door locks). Plus it was rated at 49mpg city and 52 mpg hwy and I've used it primarily for long drives from San Jose to Santa Barbara, so that stretch is very flat and perfect fot this car and it's intended high mileage purpose. If you doubt me getting 50MPG (it's a 7 gallon tank and I consitently get over 350 miles out of it, you do the math)...oh and I also have reciepts and a mileage log I can show you.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 97SS &raquo;</TD></TR><TR><TD CLASS="quote">Relax SFlCrx...the OP said, "im wondering what could be the possible cause of bad gas mileage on my 91 si."...where do you see him saying 1988 (which I do know the weight differences trust me that's why I was looking for a 1988/89 CRX HF becuase all 90/91 CRX's gained weight due to the door reinforcements and other weight add on).
Also he was incorrectly expecting to see "(like 30-40+mpg?)" so I just wanted to point to the data to show him what to realistically expect, and not knowing his mileage and quality of aftermarket components, that may seriously affect his mileage (besides the normal things, tune ups, tire pressure, tire size, added weight, aerodynamic mods, etc)
My CRX has low mileage and is completely dead stock (besides the wheels and coilovers, power door locks). Plus it was rated at 49mpg city and 52 mpg hwy and I've used it primarily for long drives from San Jose to Santa Barbara, so that stretch is very flat and perfect fot this car and it's intended high mileage purpose. If you doubt me getting 50MPG I have reciepts and a mileage log I can show you. </TD></TR></TABLE>.

lol reciepts and mileage logs, no i believe you i know of a few people getting 50-60 mpg in an hf

 

..ok we're all cool.
I just read the entire posts and I was about to suggest his short trips could be hurting his mileage.
Heck my work commute is 2 miles so my 350Z gets crap mileage when I bring it to work everyday. On the highway it's another story, it gets 29-30 mpg from San Jose to Santa Barbara...not bad for a big V6.

 

Who said the HF has a 7 gallon tank?? The gas tank on an HF is 10.2 gallons according to my original CRX owners manual, so sorry buddy you arent getting 50 mpg but more like 35.

 

Good catch there CRXperiment, I double checked my manual and you're right! It is a 10.6 gallon capacity, so there must be something off with my fuel gauge then because I only filll up when it's empty on my gauge, and when I fill it up it's always 7 gallons to fill it up, 7.2 gallons is the most I've ever been able to pump into it in over 15 fill ups, and I go off the amount of gallons I fill it up with and divide the miles I have driven, so the fuel tank capacity is not the number I use to calculate mileage, it's what goes into it at the gas station...so I'm still getting 50mpg!
I hope to improve on that by getting rid of the heavier 15" wheels it has and replace them with the light weight 13" VX wheels and hope to find a guy who can fab me up some rear tire skirts!