hooked up wideband (a/f ratio readings)

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Jan 22, 2008
MY CAR IS BONE STOCK i think rebuilt motor within last 100,000 miles (320,000 miles on the car) :)

hey guys,

i was finally able to get a wideband (hks knock amp) and get it working. the only thing is, the placement of the wideband sensor was a bit tricky. i'm not sure how much of an effect it will have on the readings. but i had to put it AFTER the first CATALYTIC converter (just before the muffler).
because the stock header/manifold are 6 into 2 and 2 pipes go into the CAT and then it merges into one AFTER the CAT.
so these readings SHOULD read LEANER than if i were to put it BEFORE the CAT. how much leaner, i am not sure...

anyway, what i got was:

idle: 13.6-13.9
(sometime it would go down into the 12's- i think i have a vacuum issue because the car would stall SOMETIME when i come to a stop/idle)

cruise: 14.2-14.7 (this was anywhere between 5 mph and 70 mph)

WOT (wide open throttle): it went down into the 12's and 11's and MAYBE some 10's.. as the RPM went past 5000 rpm.

second step that i plan on doing if possible is to get a PIGGY BACK fuel controller (apex'i s-afc2) and lean out the idle to: 15:1
and also lean the cruise out to mid 15's.

i won't touch the wide open throttle because i hardly ever do so.

but before all that, i'm planning to look for and fix the vacuum leak. see what it changs on the readings especially at idle.

then change to new plugs... then do the fuel changes... i'll record my MPG and also A/F ratio's each time i make these changes and post back up here.

as of now i'm getting an average of ~14 MPG overall per tank of gas. roughy ~300 miles per 21-22 gallons with where it sits right now.

i was hoping that it would read really rich and so i could have more room to work with!

having a landcruiser that gets 18-20 mpg would be INCREDIBLE
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That idle is rich, I would say something is wrong with the stock components. Fix whatever is wrong with stock before you go to a piggyback. For reference my 3FE idles at 14.4-5 according to my wideband (which I think is a little rich, and may lean out a bit with a Unichip if I can convince myself that all stock components are operating correctly). High 13s is definitely rich. Does it pass emissions?

Also for reference I originally had my wideband after the cat. I got advice to move it before the cat for better accurracy which I did. I really didn't see the readings change in any meaningful way. Obviously before the cat is best but based on the readings that you're seeing I'm not sure I would expect it change a whole lot.
you might check the "closed" position on you tps. I think it's that switch which triggers the ECU to use a dedicated fuel trim for idle. That's based on my OBDII experience and it might be different for you.
I really suggest the E-manage for a piggy back.

I also suggest moving the wide band to before the Cat. If it is like the innovative LC-1 it will have an extra output lead that sends out a narrowband type signal that you can send the ECU. This way the one 02 sensor can make the stock ECU happy as well as feed an accurate wide band measurement of the AFR to the gauge.

You really have a much harder time getting an accurate tune measuring after the cat. The main reason the OEM put one after the cat is to check the operation of the catalyst and throw a code if is not doing its job.

The post cat o2 reading will depend on factors such as the wear/age of the cat and even greater fluctuations occur between when the cat is cold and when it is up to full operating temperature.
i passed smog no problem but i think the car is still running rich.

yeah with the readings i found and the way my car is running/getting gas mileage, the wideband reading isn't too far off (even after the CAT).

i think if i had a vacuum issue, it may run rich for a second (which it does- when it's about to stall). only because the ecu probably see's too much air and all of a sudden dumps a ton of fuel to try to adjust for that... i'm not sure though but landtank, are you saying to check my Throttle Pressure Sensor?
is there an IACV (intake air control valve)? that would usually control the idle as well i think.

a few people told me, putting an intake and exhaust sytem will help it breathe and free up some A/F ratio's so it'll run leaner (getting better gas mileage).
TPS, throttle position Sensor, it's on the side of the throttle body attached to the throttle plate mechanism. I know that there is an adjustment in the 96 FSM for it so it would be worth a shot I think.

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