A/F Question - Toyota Yaris Forums

whooppee777 · 12-02-2008, 09:57 PM

I've noticed on my blitz rvit that when i am driving the a/f normally stays around 14 but when i come up to a stop sign or stop light and i pull the car out of gear and into nuetral to coast the a/f jumps up to 17 and stays there till i hit the brake or go back into gear. is this normal?

cali yaris · 12-02-2008, 10:12 PM

hitting the brake changes your air/fuel ratio while in neutral? hmmm.

CASTREX · 12-02-2008, 11:02 PM

It could be some kind of fuel economy feature...

largeorangefont · 12-02-2008, 11:23 PM

Yes the car is just saving fuel at idle conditions. I wouldn't worry about it.

Tamago · 12-02-2008, 11:25 PM

17:1 should throw a CEL though.. well at least it does in my car :(

Nexus1155 · 12-02-2008, 11:36 PM

DFCO leans AFR on coastdown/stop for economy i suppose that is happening? Might want to read more on it, it activates different in different cars..

whooppee777 · 12-03-2008, 12:40 AM

Quote:

Originally Posted by cali yaris

hitting the brake changes your air/fuel ratio while in neutral? hmmm.

just reporting the facts and not just in neutral but also when i take my foot off the throttle completely while still in gear too. my guess is it has something to do with vacuum.

Quote:

Originally Posted by largeorangefont

Yes the car is just saving fuel at idle conditions. I wouldn't worry about it.

thats what i thought too but y does it change when i hit the brake? if it were something bad it should set a CEL. so until it does i'm not worried.

does the scan gauge 2 give a/f readings? if so can someone with a near stock yaris or near stock yaris let me know what it reads under these same conditions?

cali yaris · 12-03-2008, 02:50 AM

I don't think the scangauge does a/f. I know the blitz r-vit does -- whoopee didn't you have one of those installed at one point?

turboyaris · 12-03-2008, 03:32 AM

its not uncommon for an AF to read 17:1 when the engine isn't under any loads. if there is no real load on the engine, the likelyhood of detonation is less, not too mention, that detonation would happen around the same time as ignition spark anyways, as the timing as adjusted too... at least this is what I have been told. It more has to do with the throttle being closed and all then hitting the brakes I presume. Is your car manual?

I know on my tune, when I accelerated it was tuned to 12:1, then if i was just cruising at speed it was around 14:1 and as you said it went above that for idle and no load situations. The reason I was told is also to clean the plugs and engine out as I guess it burns any reminant fuel that hasn't already been burned off.... if that makes sense

whooppee777 · 12-03-2008, 10:40 AM

Quote:

Originally Posted by cali yaris

I don't think the scangauge does a/f. I know the blitz r-vit does -- whoopee didn't you have one of those installed at one point?

i have the r-vit. i know not too many others do. i know more people have scangauge 2 but not that it matters considering it doesnt read a/f

richardholdener · 12-03-2008, 06:47 PM

The reason the A/F ratio changes under decel is that the injectors are switched off completely under this condition. They are switched back on to keep motor from stalling and keep idle stable. The idle air/fuel should be 14.7:1. Toyota does not run leaner mixture at idle (emissions reasons).

whooppee777 · 12-03-2008, 07:05 PM

excellent. i am completely worry free now. thanks richard

cali yaris · 12-04-2008, 02:47 AM

Quote:

when i come up to a stop sign or stop light and i pull the car out of gear and into nuetral to coast the a/f jumps up to 17 and stays there till i hit the brake or go back into gear.

it's the hitting the brake part that I still don't get. I understand DFCO conditions.

whooppee777 · 12-04-2008, 02:44 PM

what the hell is DFCO?

whooppee777 · 12-05-2008, 01:17 AM

Quote:

Originally Posted by camelll

Deceleration Fuel Cut Off. It is a fuel economy feature.

http://www.yarisworld.com/forums/showthread.php?t=4248

then in that cae...

Quote:

Originally Posted by camelll

I am assuming when he is applying the brake he is below 1000 rpm, so DFCO is gonna is gonna quit and he will see normal conditions on his a/f readings. When he puts his car back in gear again I am assuming he is hitting the gas which also will stop dfco.

Gotta love assumptions. Maybe whooppee can shed some light.

yes rpms below 1000 when braking and yes hitting the gas when putting into gear.

good to know my dfco is working properly

whooppee777 · 12-08-2008, 05:36 PM

i dont know how to get the r-vit show mpg. i see fuel economy in the menu somewhere but it needs to be configured some how i guess buuuuut the manual was in japanese. so shit

12-02-2008, 09:57 PM	#1
whooppee777 I used to have 1700 posts View User's Garage Drives: 2008 Yaris Hatch Join Date: Apr 2007 Location: Maryland Posts: 808	A/F Question I've noticed on my blitz rvit that when i am driving the a/f normally stays around 14 but when i come up to a stop sign or stop light and i pull the car out of gear and into nuetral to coast the a/f jumps up to 17 and stays there till i hit the brake or go back into gear. is this normal? __________________ *First Boosted Yaris On The East Coast*

12-02-2008, 10:12 PM	#2
cali yaris ULTIMATE View User's Garage Drives: 07 Yaris Turbo Join Date: May 2007 Location: Canoga Park, CA Posts: 14,859	hitting the brake changes your air/fuel ratio while in neutral? hmmm. __________________ Micro Image forums, online store and shop are now closed. It was a great eight year run, but it was time to focus on other things. I'm still selling parts on eBay under micro*image seller ID and customers can still make requests for anything specific.

12-03-2008, 02:50 AM	#8
cali yaris ULTIMATE View User's Garage Drives: 07 Yaris Turbo Join Date: May 2007 Location: Canoga Park, CA Posts: 14,859	I don't think the scangauge does a/f. I know the blitz r-vit does -- whoopee didn't you have one of those installed at one point? __________________ Micro Image forums, online store and shop are now closed. It was a great eight year run, but it was time to focus on other things. I'm still selling parts on eBay under micro*image seller ID and customers can still make requests for anything specific.

12-03-2008, 07:05 PM	#12
whooppee777 I used to have 1700 posts View User's Garage Drives: 2008 Yaris Hatch Join Date: Apr 2007 Location: Maryland Posts: 808	excellent. i am completely worry free now. thanks richard __________________ *First Boosted Yaris On The East Coast*

12-04-2008, 02:44 PM	#14
whooppee777 I used to have 1700 posts View User's Garage Drives: 2008 Yaris Hatch Join Date: Apr 2007 Location: Maryland Posts: 808	what the hell is DFCO? __________________ *First Boosted Yaris On The East Coast*

12-02-2008, 11:02 PM	#3
CASTREX Who said Yaris was slow? View User's Garage Drives: Yaris T-Sport 2008 Join Date: Nov 2006 Location: Costa Rica Posts: 1,287	It could be some kind of fuel economy feature...

12-02-2008, 11:23 PM	#4
largeorangefont Break'em off some. View User's Garage Drives: 07 Yaris LB, 04 Cobra Join Date: Jan 2007 Location: So Cal, OC Posts: 854	Yes the car is just saving fuel at idle conditions. I wouldn't worry about it.

12-02-2008, 11:25 PM	#5
Tamago Start another Oil Thread! View User's Garage Drives: ZZW30 Join Date: Dec 2006 Location: South FL Posts: 4,890	17:1 should throw a CEL though.. well at least it does in my car :(

12-02-2008, 11:36 PM	#6
Nexus1155 Bathroom + Laptop = <3 Drives: Audi Join Date: Aug 2006 Location: Dorchester Posts: 1,009	DFCO leans AFR on coastdown/stop for economy i suppose that is happening? Might want to read more on it, it activates different in different cars..

12-03-2008, 03:32 AM	#9
turboyaris Drives: 2007 Yaris Sedan Join Date: Jan 2007 Location: Southern New Jersey Posts: 459	its not uncommon for an AF to read 17:1 when the engine isn't under any loads. if there is no real load on the engine, the likelyhood of detonation is less, not too mention, that detonation would happen around the same time as ignition spark anyways, as the timing as adjusted too... at least this is what I have been told. It more has to do with the throttle being closed and all then hitting the brakes I presume. Is your car manual? I know on my tune, when I accelerated it was tuned to 12:1, then if i was just cruising at speed it was around 14:1 and as you said it went above that for idle and no load situations. The reason I was told is also to clean the plugs and engine out as I guess it burns any reminant fuel that hasn't already been burned off.... if that makes sense

12-03-2008, 06:47 PM	#11
richardholdener Drives: 2008 Yaris hatch Join Date: Oct 2008 Location: Las vegas, NV Posts: 183	The reason the A/F ratio changes under decel is that the injectors are switched off completely under this condition. They are switched back on to keep motor from stalling and keep idle stable. The idle air/fuel should be 14.7:1. Toyota does not run leaner mixture at idle (emissions reasons).

12-08-2008, 05:36 PM	#16
whooppee777 I used to have 1700 posts View User's Garage Drives: 2008 Yaris Hatch Join Date: Apr 2007 Location: Maryland Posts: 808	i dont know how to get the r-vit show mpg. i see fuel economy in the menu somewhere but it needs to be configured some how i guess buuuuut the manual was in japanese. so shit __________________ *First Boosted Yaris On The East Coast*

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