320km per tank economy

[R3DN1NJ4]

Hello all,

I'm trying to find the reason of such a bad fuel economy in my 2008 yaris sedan, AT,1.5 L, 105000 km.

That should be around 18-19 mpg...

i have:
* cleaned throttle body
* cleaned MAF sensor
* cleaned PCV valve and hose (had lots of gunk and was stuck, it now rattles a lot when shaken)
* changed ATF
* changed spark plugs (NGK BKR5EIX)
* checked drum brakes
* checked for error codes with OBDII and torque app.
* checked coolant temp (averages 85 °C / 184 °F)

The car is really responsive, speeds up fast, starts like new.

i have also a couple questions.

01. Does yaris have an EGR valve?
02. How to check o2 sensor? can i test with multimeter ?
03. What else could be the culprit? Catalytic converter? fuel injectors? coils?
04. Where can I find sensor reading threshold to compare ?

thanks


UPDATES:

07/12/14 - Changed B1S2 O2 Sensor.
07/23/14 - Cleaned spark plug well (had oil) scanned B1S2 voltage, still 0v.
07/25/14 - Changed valve cover gasket and spark plugs for Denso SK16R11.

[Rigaud]

How do you drive and what speed? Makes a huge difference.

I have an 09 3HB tuned, lowered, wide tires, 1ZZ TB and if I drive 95-100kph taking it easy I manage to do 5.4 to 5.6L/100km

[R3DN1NJ4]

i drive even slower, average 65 or so km/h. city driving 90% of the time. i do hit 90s from time to time but try to keep revs around 2000-2500 when doing so.

[R3DN1NJ4]

I have changed the B1S2 O2 sensor, it was not reporting anything, when graphed a constant 0 was the value. I however keep experiencing the increased fuel consumption.

Any ideas?

[nookandcrannycar]

city driving 90% of the time

:eek:

[IllusionX]

city driving + high heat = very bad fuel consumption.

Also, what grade oil are you using?

[R3DN1NJ4]

city driving + high heat = very bad fuel consumption.

Also, what grade oil are you using?

Yeah, Panama is hot, however some folks do 450-500 km per tank.

I use 5W-30 oil, been thinking to change that to 20W-50 since we don't have winter in here and, believe I should adjust oil viscosity to a warmer place.

I did notice that one spark plug had some oil on it, not from oil changes, so, will check if the rest are in the same condition.

old spark plug (3 or so years old) DENSO: http://imgur.com/iJ2NEXd
"new" spark plug (4-5 months old) NGK : http://imgur.com/BFVWvmt

planning to change the valve cover gasket. first time ill do so. any guides?

In the event that I find gunk inside, how should i go about cleaning it. Also, should i use carb cleaner to clean spark plugs?

Thanks

[trunkout]

oil on the spark plug? I think you found your issue....

[R3DN1NJ4]

what should i do about the oil? how do i clean that?

[trunkout]

if you have oil on your sparks plugs "cleaning" isn't going to fix the issue. take it to a mechanic.... unless you wanna tear down the motor yourself!

[why?]

city driving + high heat = very bad fuel consumption.

Also, what grade oil are you using?

actually heat equals better gas mileage. Some of the crazier ecomodders route their intakes to get air from the hottest parts of their engine bay.

The hotter the air, the less dense it is, the less gas the car uses to mix with it.

[R3DN1NJ4]

I have scanned for B1S2 O2 voltage and it is still reporting 0v, even after changing it for a brand new one from Toyota.

How can I check if the circuit is the culprit.

I have cleaned the spark plug well (only one had some oil on it, the other 3 looked very good) and will change the gasket in the coming days.

I might have just spent $120 for nothing if the wiring harness is the culprit. So, how do I check that this is OK?

I compared to a 2001 yaris (that does the 500+km/tank) and that one did report a value for the B1S2.

Thanks for the help so far.

[Bluevitz-rs]

B1S2 is supposed to read 0V. That means you CAT is working properly. You wasted your money on that one.

[R3DN1NJ4]

What else could be? Custom tire size? I run 205/40/17.

Don't know what else to think :s

This is the B1S1 voltage reading at idle, does it look OK?

http://img.tapatalk.com/d/14/07/31/y8uha9am.jpg

[IllusionX]

Try using 175/65R15. The 17" kills your mileage.

[Bluevitz-rs]

Was going to suggest smaller tires too.

And yeah. B1S1 looks normal. They go rich lean rich lean.

[R3DN1NJ4]

Thanks for the advice, I do not have 15s since this one was the most basic trim, in Panama they come (or at least used to come) in iron 14"s. So 175/70/14 if my memory does not fail me is what I have. Will test with those tomorrow, fill up, and report when the tank is half empty.

Once again, thanks for helping me out with this. Very much appreciated.

[Bluevitz-rs]

14s are even better. Smaller lighter wheels take much less power to turn.

[IllusionX]

Thanks for the advice, I do not have 15s since this one was the most basic trim, in Panama they come (or at least used to come) in iron 14"s. So 175/70/14 if my memory does not fail me is what I have. Will test with those tomorrow, fill up, and report when the tank is half empty.

Once again, thanks for helping me out with this. Very much appreciated.


Are you saying you are doing 320km with a half tank?

[R3DN1NJ4]

Are you saying you are doing 320km with a half tank?

Not at all, 320 km full tank, hence the low fuel efficiency , I wish I could do that!

What I mean is that half tank or even a quarter will do to test how much it's consuming.

Roughly it's about 40 km per bar on the dash, 8 bars equal 320 km, more or less what I get.

Also I noticed that driving like I just stole it, and driving slow do not make much of a difference for me, 10 km less per full tank for aggressive driving and hard stopping on the city.

[jambo101]

I have an 08 sedan and usually fill up when i'm down to 2-3 bars which is somewhere between 300-350kms. I find kind of tires and driving style can make major differences in fuel consumption.

[R3DN1NJ4]

I have an 08 sedan and usually fill up when i'm down to 2-3 bars which is somewhere between 300-350kms. I find kind of tires and driving style can make major differences in fuel consumption.
That's what a normal behavior should cause, that driving style impacts consumption, and that less rolling resistance translates into less effort to move, but on my case, as long as the engine is running it seems to burn the same amount of fuel...

You do like 60-70 km per bar, while I do just 40.

[IllusionX]

the fuel gauge is not linear, you cant calculate it like that.

like i said earlier, it is best to fill up, drive it, fill up again, and then calculate how much you've driven to know your fuel consumption.

If you are always in city traffic, have AC on, and the combination of your 17" wheels, i think your car is fine.

my 1st bar goes away around 60km when i have ac on and driving mostly city stop and go with speeds reaching 60kmh for max efficiency when possible.

[R3DN1NJ4]

after two tanks with the stock tires nothing has improved. I'm halfway through the third
http://tapatalk.imageshack.com/v2/14/08/13/6928cd8b537c19739ae7f73c7bdf8021.jpg

[jack black]

The OP didn't volunteer the most important info: what is the length of trips and how much idling involved?

[R3DN1NJ4]

The OP didn't volunteer the most important info: what is the length of trips and how much idling involved?
I do about 35-40 km a day, and idle only on stop lights...

[R3DN1NJ4]

I found this today, never reported as error before, seems like my catalytic converter might be the issue, could be plugged.

http://tapatalk.imageshack.com/v2/14/08/19/b62a8b2d1a9ef11db880ea5b45eaec55.jpg

[IllusionX]

Well, here you go