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]

Originally Posted by R3DN1NJ4

city driving 90% of the time

[IllusionX]

city driving + high heat = very bad fuel consumption.

Also, what grade oil are you using?

[R3DN1NJ4]

Originally Posted by IllusionX

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?]

Originally Posted by IllusionX

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?

[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.