neozero999

hey guys ive been noticing my car has been getting some pretty crappy mpg lately, i filled up about a week ago and since then ive driven about 170 miles, and im already at a little above quarter tank!i know i should be getting better mpg than that! i recently did a full tune up, checked up on my timing *fine* but i guess my problem could be my o2 sensor, but would it give me this bad of mpg? i checked all the lines on the charcoal canister and everything checked out. im guessing if i were to use up all the gas in my car my mileage would probably around 275 a tank... car has around 130k miles. thanks guys for reading!

adeline

getting any ecu codes?

ef yu

change your fuel filter. changed mine and i got like extra 10-15mpg.

grog

if you want to find out your milage CALCULATE THAT ****, gallons pumped divided by miles traveled. stating how far you go on a tank is not accurate at all, you need some exact numbers to get MPG. telling us miles per tank fails to accuratly gauge the amount of fuel used, you have to guess, using tank capacity negates the fact that you never completely run out of gas.

if you want us to be of any help, you will need to provide actual MPG.

set you trip meter the next time you fill up the tank, then the next time you fill the tank, write down the miles traveled, and the amount of fuel you just pumped. then divide miles by gallons. then we can gauge your milage

HT Chaplain

o2 sensor can make a big difference! I usually go 400 before filling up with my hf

SIred91

Deffinately change the 02 and fuel filter, if you know your timing is correct, than that should be your next move.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dustin_Pierce &raquo;</TD></TR><TR><TD CLASS="quote">Are you beating on it and revving like crazy? If no, check the o rings on the injectors that snug on the fuel rail. I found out two of my four o rings were cooked and fuel slowly leaked around the injectors. </TD></TR></TABLE>

hyahahhahahha........You can beat on an HF all you want and it will still get better mileage than a DX or Si.

neozero999

well the tripometer is 171 miles on it, and the last time i filled i filled 7.1 gallons *im guessing theres a reserve of 3 gallons?* and by that guesstimate my average mpg would be 22.8 mpg... *my guage reads quarter tank, but we all know how that pin tricks us and goes up and down depending on elevation and how rough you are on the gas*im definately going to change the o2 sensor, and fuel filter asap. thanks for all the help!
some calculations i used:
gas i consumed: reading from guage: 3/4 tank, 7.2 gallons
miles i so far gone: 171 miles

ef yu

that reminds me, i have a bad o2 sensor too..only getting like 270 on a whole tank. hmmmmmm *goes to ebay and buy a new O2*thanks hahahah

avrfan

I have an 88 Crx HF which was getting 40-53-mpg depending how I drive and weather and road conditions however I never seen it get less than 33mpg even when running it hard like 95-100MPH on the highway...

This winter I been driving in below freezing and subzero climate in North Dakota. Temos frequently below -20°F. I started to get a CEL and I kept driving. it would come and go. However my fuel economy dropped as low as 20mpg! When the car is cold an idling up at start up, I can smell the exhaust is rich as it should be on cold start up. Eventually I pulled the carpet back and counted the LED Blinks for codes 1,7,&20. Those I believe are for O2 sensor, TPS and ELD. So I replaced the o2 and TPS sensors, the ELD I didnt have a replacement but I don't see how that would hurt the gas mileage.

anyhow, the TPS fixed the throttle deadspot but I did notice the CEL came on and blinked out O2 and ELD again, I fiddled with the plug connector and also did the voltage test on the o2 according to the factory manual and it was as expected. after that the code for O2 cleared but the fuel economy still suffers.

The engine has a never ending surge and drop with slightly elevated idle speed 1100-1200rpm. The coolant was a bit low I topped it off and bled the air out. I noticed this idle surging bouncing idle occurs mostly when I have the headlights on and especially the more electrical loads I'm running the worse it bounces. so I believe it has something to do with the ELD or ECU.

Any how I'm now getting around 26-30mpg and that's driving quite conservatively.

once while idling the car in the driveway for an extended period, I smelled raw gasoline around the front of the car, so I think I , might have a fuel leak, I didn't have time to check then but I ran the car another day for a while and looked around under the hood and found no obvious leaks.

How can I be sure that it's not leaking fuel?

What else can I do to get the gas mileage back to normal? I think it's running too rich because of the cold weather here...

it's there a way to monitor the fuel mixture or o2 signal to determine if it's running too rich or the ECU thinks it's lean all the time?

Thanks

====== Update: 8/18/2016 ======
Here is some good info I found that explains why cars get poor fuel economy in subzero temperatures...

1. More idling

This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.

Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).

2. Low tire pressure

Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).

3. Increased rolling resistance

Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).

4. Crappy road conditions

It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)

5. Lower average engine temperature

In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.

A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).

Also related...

6. Higher average lubricant viscosity

Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.

Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.

7. Weaker gasoline

Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)

8. Higher electrical loads

In colder temps, you use electrical accessories more often:

- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)

9. More aerodynamic drag

No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).

A vehicle’s aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% (source).
http://www.metrompg.com/posts/winter-mpg.htm

sstupid

Here's my same thread on this:

https://honda-tech.com/forums/showth...hlight=mileage

I still haven't fixed my exhaust, so I don't have a remedy yet.

avrfan

ok, the CEL is off however. I am still getting codes 1 & 20 on the ECU. I also checked and found that 2 of my injectors are a little wet with fuel. it's not visibly dripping or leaking profusely when idling however perhaps under load it might be significantly worse. I can't imagine that it's leaking that much fuel per hour though. basically it would have to leak as much fuel as it is burning to bring the economy down to 25mpg. Maybe that's throwing the fuel mixture off and the o2 sensors detects the lean condition and the ECU enriches the fuel mixture this burning even more fuel...

why am I still gettin code when ive already replaced the sensor?

thanks

avrfan

Thanks, I read your thread, and posted my story there. My fuel economy has been sporadic but mostly 38-43mpg. However lately it has been at 32.5mpg for the past 2 tanks and its fouling my spark plugs up pretty badly. I noticed the fuel pressure regulator didn't seem to be holding at 35psi after priming (engine off key on) so I replaced the FPR (its running smoother now and more powerful) I also picked up a used MAP sensor, yet to be installed. I found my PCV hose is plugged and collapsed under vacuum at idle. I have to fix that (maybe the main reason for the fouled plugs and oil loss( blowby at rings and valve guides and leaking rear main seal )

I will try and post back what I figure out. The only code I am getting is code 20 for ELD. I recently replaced the O2 sensor because I thought my discount ebay one was a manufacture reject so I got a new one to eliminate doubt.

Thanks

Former User

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