what's the difference?............. i was cruzing the search button looking for info on a surging prob that i have right now and i couldn't figure out if the AFR sensors were on the new mods of tacs and runners or if they were replacements for the O2 sensors.

lil history for the surging prob if you wanna throw some suggestions.
99 tac 4x4 v6 120k miles. getting some surging after the engine is warm (it's quite cold natured now). mostly it occurs around 2k or 2500 rpm. very repeatable and it has a cresendo pattern. no change in the rpms, just a loss of power intermittently, but with a steady pattern. i've had an injector and intake flush (run the truck on chemicals for an hr), upstream and downstream O2 sensors replaced, fuel filter replacement, TPS replaced, cleaned the MAF sensor a couple of times, listened for vacuum leaks. changed plugs, cleaned the throttle body, fuel pressure is good but alas..........still surging and cold natured. i've also got a bank one lean code as well. sound like injectors? fuel rail probs?
thanx
brad

 

AFR is just toyota's confusing name for the front O2 sensor, and then they charge like 3x the price for it.

How did you clean your MAF meter? Need to do that on mine...

 

If you're still getting a bank 1 lean code, then it's some part of the air/fuel delivery system that is causing the problem. My best guess would be the MAF itself is bad. Cleaning it won't do any good if it's not supplying enough voltage for the amount of air that is entering the engine. Buy a new one. They're about $100.

As for the difference between the Air/Fuel Sensor and a standard O2 sensor: There is a marked difference between the two. The A/F Sensor outputs a linear voltage based on the A/F Ratio. At Stoich, or 14.7-1, the output is 3.3V. At richer A/F ratios, the voltage decreases linearly and at leaner ratios, the voltage increases linearly. It is also more sensitive and accurate than a standard O2 sensor.

Starting in 1999, models destined for CA had the A/F Ratio sensors and two (2) Catalytic converters.

Hope this helps.
G

 

bamayote, did you resolve that : po171: code- fuel too lean. my 1999 ltd 3.4liter check engine light came on, i pulled the code po171 fuel to lean. i pull out the maf sensor and clean it, put it back in and cleared the code using a scan tool. next day check engine light came back on again code po171, this time i clean the throttle body and clean the maf sensor again, put about 44 miles on and so far no check light. i hope i dont need a front 02 sensor.

 

yeah, what he said

by the way, Dr. Z, the SMT6 works a lot better in my '99 5 speed. still some minor problems (it idles too low unless i jack up the fuel zero), but it is much better than in the 2000. i'll post more on that monster thread when i get more info.

creed

 

Hey Creed! Good to hear. You know, since
this thread is about the AFR Sensors...

I was thinking of a way for you to use it to monitor your A/F Ratios for tuning purposes. It seems that about 2.5V Volts on the sensor output wire = 12.5-1 AFR. So, using a digital volt meter attached to the AF1+ wire at the ECU, you tune your WOT maps on the SMT-6 until you get a 2.5V reading. You could even use it to monitor your Closed Loop AFR as well. Heck, if you wanna get really clever, get a dash mounted Digital Voltage Gauge.

Check out this article for more clarity concerning the voltages I mentioned. There is a chart down the article a ways. If it works as I think it ought to, it would save you drilling a hole in your headers/exhaust manifolds.

Just a thought. Lemme know what you think.

G

 

yeah, Louie and i discussed this a few months ago - he seemed to think that the signal was balanced, though, with a seperate refernce other than ground. maybe not?

anyhow, doesn't do me any good now, because my *new* truck (the '99) has an EGO sensor instead, which i like because you can use the ESC to slip it into open loop for easy tuning

creed

 

Well, there you go then.

G

 

Boss hog.............i'm still getting the lean code and getting alot of cold natured crap from the rig right now.
i had it in the shop for my mech to look at and he said he was getting good data streams from both o2 sensors and maf sensor........basically to all the components i was asking him about i had also checked the maf sensor with a voltage meter and it seemed to within the voltage limits outlined in the chilton manual..................
i hope i'm not arguing with you guys, that's certainly not my intention..............i'm just stumped!


thanx guys for the info! i may just try a used maf or something, who knows, i may get the gumption to get a new one...lol

thanx again!
brad

 

bamayote, check engine light has been off for 2 days now(po171) code, engine was running fine even with the lean conidtion code, the frist time i only clean the egg shape element in the air mas flow, second time i clean it i used wd 40 and clean deep inside the the maf ( element thats not visable unless you look deep inside) i used a q-tip to clean it, and then used compress air to blow it out. good thing you have the v-6 and not the 4 cylinder engine, conicelli toyota wants over 400.00 dollars for the 4 cylinder air mas flow meter and only 107.00 dollars for the v-6 mas meter. good luck . Eddie :pig:

 

Use some electrical contact cleaner and a Q tip for cleaning the MAF.
Also be very thorough about how well you clean it.

 

i'll try cleaning it again..................... i also saw a thread related to the "hot wire" that needed to be cleaned. i've never touched the hot wire, but i'll give her a go.
i'll let you know if i figure it out.

thanx again for all the replies
brad