Two issues on V-6; pinging under load with 91 octane and hesitating from idle (no load).

Lambda is front, no? Upstream?

 

http://www.ngkntk.co.uk/index.php/technical-centre/lambda-sensors/what-does-the-lambda-sensor-do/

 

My Ultragauge lists the lambda sensor as O2 sensor 1 and the other one as O2 sensor 2.

 

Ugh. Now im confused. I thought the lambda sensor measured catalytic converter efficiency. Not regulate air/fuel mixture

 

I'm pretty sure it's the other way around.

This would explain why I am not throwing a code since the front sensor is almost always reading exactly 1.000.

So at idle, the ECM is leaning things up to achieve the perfect mixture. Under load, it is richening things up to achieve the perfect mixture. It's doing it's job.

I think my problem lies in the transition and that's why am getting that hesitation when I stomp on it.

 

Lambda sensor = A/F sensor = wideband sensor = bank 1 sensor 1

California spec cars have these because of what i said before, we have more variations of fuel types at our pumps than any other state. The rear O2 is always a old school zirconia narrowband 1V sensor.

 

See heres some confusion, in the first set of pics on this thread, the lambda sensor is showing at 1v. While the bank 1 sensor 2 is showing .77v.

But here youre saying the narrow band is what runs at 1v.

 

@CodeSeven,

The front sensor will never show you the raw data of what is in the exhaust based on a rich/lean waveform. The output is based really on 0V being stoich, with negative voltage being rich, positive being lean. We just see that based on a 1.000 axis. The 5V supplied to the wideband sensor does not act as a reference as the 1V in a narrowband sensor. It is really there mostly to power the internal heater. These fuckers need to be at over 1300F to operate properly.

In a way, the wideband sensor operates like an oscilloscope where a narrowband acts like a voltmeter.

I know i usually say that you will only see the reference voltage when looking at a wideband sensor on a cheap scanner, i just avoid explaining things in depth when i dont have to. You really are seeing the ECU interpretation of a stoich signal, not the actual voltage that is being applied, in either a negative or positive polarity, to maintain Lambda (neutral or 1.000) within the Nerst cell, the section between the reference cell and the sample cell. This may show up as 1.0 or 0.5 on your scanner if its not designed to read the sensor output properly. Thats because many cheap scanners will round this number to 1.0.

You see the reference oxygen amount in a narrowband zirconia sensor is based on the 14.7:1 a/f ratio of gasoline (HC) to oxygen (O2).

The reference oxygen amount on a wideband Lambda sensor is 20.95:1. This is the amount of oxygen content in the reference air of Earth.

The catalytic monitor (Bank 1 sensor 2) should be reading almost near zero when NO LOAD is on the car. It is expected that the car will rich up to accelerate, but the ECU should be dialing back as engine demand is leveled off, even if it levels of at 4000RPM, it will back off some from the time you smashed the pedal down. This is based on a 1V reference.

I think i read that E85 actually is actually stoich at around 9:1, similar to alcohol fuels. A regular zirconia sensor would be telling the ECU to flood the engine, as its calibrated for a engine management system to put 14.7 and only 14.7 parts air to a measure of fuel.

 

A quick question that is somewhat relevant...why two MAF sensor readings? My understanding is that there is only one sensor.

Is the second number adjusted for temperature, elevation, etc.?

 

Ma2 is a calculated reading. Ma1 is an actual reported reading. Seems like your truck thinks its getting more air in than your maf sensor is saying. Indicating more of a vacuum leak than bad maf.

 

Which seems right since ma2 is at 30 and ma1 is at 26, thats about 14% more air coming in being calculated. Which is what your fuel trims are compensating for. Vacuum leak.

 

I changed the MAF sensor today and...















Wait for it...













OK, so I have company and couldn't spend enough time driving for a full assessment, but so far the numbers and drivability are encouraging. Trim number are in the single digits idling and under heavy load. The engine is 'vrooming' between shifts as I am used to overcompensating for the hesitation.

But I'm not going to get too excited until I've driven it for a few days.

 

Boooooo company

Yaaaaay Taco

You did pull the battery cable to reset everything, yes? Youll need to drive around at least long enough for all the OBD monitors to complete before you can say what effect the MAF has had.

 

Affirmative.

And yes, I agree on the drive time, which is why I ended with the 'But...' statement.

 

I watched a video about fuel trims on a jetta. The fuel trims only took a minute to calibrate after deliberately causing a vacuum leak and stopping it. Fuel teim wise, you may not need to worry about resetting the computer.

Just a thought

 

Even though I pulled my battery cable to reset the computer after the MAF change, I tend to agree with you and here's why.

The other day I disconnected my old MAF sensor to see how it would idle and drive open loop. Of course it threw a check engine light and two codes. It also drove horribly. So after about a mile of driving I plugged the MAF sensor back in and cleared the check engine light. The trims returned to their previous double-digit values almost immediately.

 

Theres some freaky stuff on that youtube. Just sayin.

Knowing now that these wideband sensors are commonplace, the whole concept behind open loop/closed loop is now pretty much mute. Regular old O2 sensors relied on the thermal energy from the exhaust to being the zirconia ceramic element up to 500-600F to operate as a semiconductor between the exhaust and reference air. The 1V supply was there for a reference.

With the 5V supply on wideband sensors exclusively for powering the heating element to bring these sensors immediately to +1300F, the fuel control system does not have to rely on the availability of information form the O2 sensor.

Where it could take a few minutes for the older Tacomas to go into closed loop. A new 3rd gen Tacoma, or any other modern car, will be in closed loop at cranking.

 

let us know if the MAF is eliminating your pinging issue too. If it does, I may need to try this.

 

oh for tacoma's sake, will you tell us the result already?

 

Roger that.

Was sick today and didn't take her out. Yesterday I drove 5-6 miles for a grocery store run. Still had single-digit trims but barely got her warm enough to really check things out.