BAD Fuel Mileage.

[Ayeobe]

Okay, so.. for the last week or so, i have noticed (because its quite hard not to notice) that my gas mileage has totily plumetted...

Okay, bear with me here, im gunna talk metric, cause its just.. how my dash shows it?! so, yeah..

Filled up a few days ago. 91 octane, as per said in the owners manual (thanks to gas prices droping like mad, i was happy to put it in!)
I reset the trip odo, and drove off with a full tank of gas.
the needle is sitting just above the half-tank level, with 142kms on the odo.

So, thats roughly 25L/150km.

This started when it got cold out. About a month ago i drove 500 km to Ottawa and back, coulda gone there and back withought so much as glancing at a pumping station (if it wasnt for having to clean my headlights and windows) if i filled up in Montreal.. but, i filled in Ottawa for the lower price. I beleve i took 3/4 tank for 550km. This was going 110 to, an un-willing 150. YES. the car did go 150...though, it wasnt too pleased. (the lead car was freakin' gunnin' it. bugger.)

Anyway, pushing it, i got 500km out of 3/4 tank, and now im stuck with 141km out of half. kinda... bad.

I havnt changed anything since that trip, only thing that has changed is the temperature.
Sometimes i idle low, like 300-100rpm, but it dosnt stall. itll stay like that for a little while, then shoot back up to 800. If i press the gas again, itll come back down to 300-100 and then do the same... waits, then back to 800. I dont think that vaccume-controled "arm" that holds the throttle a little bit open works right, but im wondering if that would cause super-crud fuel economy. Havnt been able to test fuel pressure or regulator, because i dont have the adaptor for it.. so, waiting for next week, i hope.
Sparkplugs/wires are new, injectors seem new.

heh sorry for kinda-long post. Thanks in advance for your help, guys. This is money out of my pockets that gets me absolutely no-where, and would defenetly best be spent buying shit like the tie-rod end and upper-table balljoint for the left front, instead of for gas that seems to vanish. heh.

[2oodoor]

:tongue:I would check the distributor igntion timing, next the coolant temp sensor for ECU.
If the car never had the O2 sensor(s) replaced, that is a a good thing to do to, that should be a maitenance item after 80K miles or more.
Of course, air filter because of the seasonal change.
Oil change..tire pressure, alignment.. the usual things to make it roll easier. Check the trunk for excess heavy clutter, even a 80-100 lbs of junk can slow these cars down a wee bit.
Im leaving something out here but I am sure somebody will chime in with it

[bullard123]

Yep I think it needs a tune-up. Spark plugs , spark plug wires, maybe a vacum leak as well

[Dr_Snooz]

:tongue:I would check the distributor igntion timing, next the coolant temp sensor for ECU.
If the car never had the O2 sensor(s) replaced, that is a a good thing to do to, that should be a maitenance item after 80K miles or more.
Of course, air filter because of the seasonal change.
Oil change..tire pressure, alignment.. the usual things to make it roll easier. Check the trunk for excess heavy clutter, even a 80-100 lbs of junk can slow these cars down a wee bit.
Im leaving something out here but I am sure somebody will chime in with it

Of course we're all gonna chime in! :lol:

Couple thoughts:
- Roodoo is right, if you aren't keeping the car up, that's the place to start
- After that, most of what I've read on here (haven't experienced it myself) is that you'll know you've lost an O2 sensor by a steep drop in fuel efficiency.
- Measuring mileage like you are doing is a very inaccurate way of doing so. Measure from a full tank to the next full tank. Take your liters off the gas pump at the next fill up
- Fuel economy drops off exponentially as speed increases incrementally (ie: the faster you go, the worse mileage you get).
- I need to change my O2 sensor

[Ayeobe]

Okay, i dont know if i said it... so here goes?!

New wiers, and spark plugs were installed a few months ago. New air filter too. oil change was done a month or so ago.
I do have tons of shit in the car, but no more then usual, or before. Didnt add anything to it since the mad hike in fuel ussage.

Tire pressure will get regulated probabily tomorow. Theres defenetly no vaccume leak.. its actualy got tons of vaccume lol.. like, at the high? (aka more vaccume) side of normal.

I should change the fuel filter. I supose ill do that tomorow.
Ill also inspect for leaks that smell like gas. Maybe its leakin in the return? that shouldnt have much pressure in it, so it wont realy spray all over the place.

Thanks for the help, guys.

[piter]

Ayeobe, I have found yout thread. Did you manage to find the solution? On my Prelude with B20A1 engine I'm experiencing since October 2008 similar problems that you have.

Last summer, while I was driving in city conditions, gas consumption was steady between 9,5-10,5 liter on every 100km.

In winter it had grown up to 12-13 liters / 100km which is rather usual due to the cold conditions. But now, we have summer and nothing has changed. It doesn't matter if I drive gently or push the accelerator pedal hard - I always get between 12-13 liters on 100km. Something definitely is wrong but I have no idea what.

I have replaced fuel filter (brand new Honda oem) and the sparks. Injectors are ok. Ignition timing was set up. Tires pressure is ok. I don't have excessive load in trunk ;)

[jasonrebellion]

i just noticed the haynes manual has no mention anywhere what so ever of an oxygen sensor......not very complete huh......

[piter]

i just noticed the haynes manual has no mention anywhere what so ever of an oxygen sensor......not very complete huh......

not all of the engines have one. My Prelude BA2 for exaple doensn't have it nor cat conv - in Europe, only type KX (Switzerland) had it. I don't have knowledge how it's with Accords.

[ecogabriel]

Ayeobe, did you solve your fuel consumption problem?
I had some issue with fuel consumption but not as bad; it turned out that the thermostat was stuck open and thus would not get into closed loop.
Solved it and it gives about 22 miles per gallon on mostly city driving with A/C on (20% highway, 80% city). Translated into metric that would be about 180 km with 20 liters of regular gas.
One thing I did that most don't do is taking my injectors to an off-car injector cleaning service. They put them in a machine and check for amount of fuel delivered and spraying pattern, then clean up and check again until they are about 2/3% of one another. That alone gave about a 15% improvement in mileage -that before catching up with the thermostat issue.

[jasonrebellion]

i need to change my o2 sensor. im getting like 20 mpg on mostly highway driving. also getting shitty get up n go til i hit about 2500 rpm

[ecogabriel]

i need to change my o2 sensor. im getting like 20 mpg on mostly highway driving. also getting shitty get up n go til i hit about 2500 rpm

Make sure the car gets hot enough to enter closed loop; I had some issues (temperature sender working randomly) before catching up with a stuck open thermostat. Once I solved that the car started being more efficient. Before that I would not get beyond 18-19 mpg highway.

[charliekuney]

Have you been putting the same amount of gas in your car, or the same price? If you put $20 in each time, you must know that gas prices are rising and you wouldn't get nearly as much gas. :)

[Tomisimo]

ok, just so you know, the most economical speed is 90km/h or 56mph. I done 500mils yesterday and did afterfill my tank today I got 6.2L at 100km with a full car with my things and neverthe less drove in mountains with 5 6-11% climes up over mountains.

Anyhow, check your O2 sensor yes, and see if you dont have ant hose leeks anywhere, with that pore milage it sounds like you have a meager fuel leak one place..
I will also address attention on your idle speed, there is a small valve behind the intake manifold, it hat 2 philips screws, inside under the lid is cold air valve, you can adjust iy by turning it.. it will adjust your idle speed.

[ecogabriel]

I did a check on my car the other day to see how much I would get in all highway driving; it gave about 30mpg at 65mph. The car is an automatic.
That was only one try; I would expect figures to vary about 5% around this number.
Translated into metric units that would be about 12.7 km./liter, 253km./20 l., or 7.9L/100km

City driving figures were almost 19mpg (18.9) with A/C on. That translates into 8 km/l., 160km/20l, or 12L/100km.

Those numbers are in the ballpark of what EPA has tested for US cars. Maybe a 5-speed would give me slightly better numbers.

[Dr_Snooz]

My '89 auto was giving me 35 mpg at 75.

...before I burned up that engine...

...oops.