Toyota ECU & Rear O2 Sensor

I have a weird problem with my EFIE not allowing my Air Fuel Ratio to run lean. I can tweak the first O2 voltage to make it lean the Gas ratio however after 4 or 5 minutes, it re adjusts itself to run rich.

Im in the middle of tweak the MAS air flow sensor to make it seem like its getting less air.
Also I placed a EFIE on the rear O2 sensor to make it seem like its running rich to compensate for the lean burn.
Both aren't getting results, Im using a A/F gauge to judge the ratio, after adjusting it shows a lean mix but after a while its bounces at 14.7 again

Anyone else have problems with this? This is on a 03 Toyota ECU 1ZZ engine

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Re: Toyota ECU & Rear O2 Sensor

WarMachineXX's picture

It seems like the Mass Air Flow Sensor Trick is working for now. Air flows thru it in the intake to warn the ECU how much air to expect. I taped up the while a bit to make it think its getting less air. it looks like the mileage jumped a bit but too early to tell.

So far I got the EFIE on the rear O2 Sensor running at +.350v & the camcom adjusting the front A/F ratio about -1% at 3000 RPM

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Re: Toyota ECU & Rear O2 Sensor

WarMachineXX's picture

New week new tests.

New tests was

Covering Up the Thermometer on the MAF Sensor
-Terrible Choppiness, the car never felt so lumpy, Air Intake Temp was fooled up to 130 degrees

Cutting an Extra hole in the MAF sensor
- No real difference but mileage seem to dip, A/F ratio maybe went richer.

O2 Defouler + Efie - Voltage (efie turned around backwards can take away voltage)
- Associated with the mileage dip. Removing it this week to see if things go back up.

O2 Defouler - Efie + Voltage
- Good mileage A/F Leans for a slight second when adjusted with positive voltage.

Next week im trying half a defouler & the MAF sensor tweaks to see if I get anywhere. Half the defowler just walls off the sides of the rear o2 sensor instead of of leaving a 1mm circle hole on top of it. Allowing more air to possibly go thru the top , maybe it will change things

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Re: Toyota ECU & Rear O2 Sensor

E=mc2's picture

If you can stand the hype...this guy claims to do real well with a Toyota...has the details need...

http://water4gas.com/2books.htm?hop=rosgio

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Re: Toyota ECU & Rear O2 Sensor

yahshua-First's picture

Your 2003 Toy. probably has an afr sensor for the front sensor , not an o-2 sensor. I found this out the hard way after ordering a o-2 controller that won't work afr sensor cars, like my 1zz engine 2005 pontiac vibe/matrix clone.
Heres a link to a forum that is studying this problem, as far as i know none has conquered the problem yet. http://www.fuel-saver.org/Forum/showthread.php?tid=1128&page=1em
rick

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Re: Toyota ECU & Rear O2 Sensor

qsiguy's picture

Ok, first, as others have mentioned, I'm 99% sure that model will have an AFR sensor which does not work the same as a standard O2 sensor. Unfortunately I have not personally worked on a vehicle with the AFR sensor so I can't offer advice on how to do it. I did come across a company who has a device they claim will allow you to lean an AFR sensor. Here's the link.

http://www.urdusa.com/product_info.php?products_id=1230100028

Second thing...

WarMachineXX wrote:

.....Im using a A/F gauge to judge the ratio, after adjusting it shows a lean mix but after a while its bounces at 14.7 again

Exactly what type of "A/F gauge" are you using for this and where did you connect it? An aftermarket wideband with it's own sensor is the only way you will be able to monitor this. If you have a gauge wired up to your OEM sensor (at the ECU) of course it will settle to 14.7. When you offset the voltage to the ECU it is supposed to readjust to what it believes is an A/F ratio of 14.7 when the actual ratio is slightly higher. Also, the OEM sensors are typically not an accurate measurement of the actual A/F ratio using the common "narrow band" A/F gauge.

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Re: Toyota ECU & Rear O2 Sensor

yahshua-First's picture

http://www.urdusa.com/product_info.php? ... 1230100028

This looks good for toyota/w map sensor. Do you know of similiar programmer that will work for vehicles w/no map sensor? such as vibe/matrix...

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RE:Toyota ECU & Rear O2 Sensor

jeff_ronalds's picture

Actually there is.. I mean this method needs a lot of adjustment as well as modification on some toyota parts and you probably need few toyota oem parts for this.. Good luck with it mate.

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