AFS Sensor

Dears,

I tested a Toyota Camry 2012 LE USA Version. I snapped the pedal and increased RPM rapidly while watching AFS Sensor (1) equivalence Ratio. The o2 reaction will never go rich. Min ratio is 700.

Meanwhile I have checked Fuel Pump Waveform which is nice and even and showing 8 bumps in 10ms.
All injector are tested using Fuel Tester and cleaner machine.
The sensor is responsive.
No MIL
MAF is good
TPS goes to 4.9V
the car doesnt have desired powered.


Any suggestion is highly appreciated.

A quick snap in park or neutral may not be enough for full enrichment. You need to put it in gear and drive (or power-brake) at WOT.

Have you checked exhaust back pressure?

I'm with pole71, you'll need to put the engine under a bigger load to see changes in the equivalence ratio.

I'd suggest going for a test drive and winding out first and second gears at WOT while watching Equivalence Ratio and Commanded Equivalence Ratio. They'll never EXACTLY agree, but the Equivalence Ratio should drop below 1.0 while at WOT. If the engine is getting enough fuel, the ratio should show .9 or less. If it stays positive during the WOT run, that's a problem.

You can also look at the A/F ratio sensor current PIDs. They should drop negative while at WOT, indicating a rich condition. As an example, this is some data I took off an '06 Tacoma with a similar sensor setup. Different engine, but the basic principles are the same.

Thank you all,
I did WOT while driving. The car doesnt accelerate as it should. For better understanding, I take a snapshot of the screen during WOT.
I have not checked exhaust back pressure.

Is there a way a scanner can indicate exhaust back pressure? Something to analyze to indicate backpressure?

Thank you all for helping me.

Can you post that snapshot of your test drive? Would love to compare it to other vehicles I've seen.

Checking for backpressure with the scanner alone is tough. The best thing I can recommend is making sure the engine is getting enough fuel at WOT (the equivalence ratio PIDs), then moving to backpressure if we don't see an issue with fuel. It's worse in your case, because your engine doesn't have an EGR system, and therefore there's no quick/easy way to check backpressure without removing an O2 or using an in-cylinder transducer.

You can sometimes use fuel trim to find a restricted catalytic converter on one bank, but the restriction has to be severe in order to produce a meaningful change in trims. In those cases, the bank with the restricted converter will show very negative trims compared to the other bank.

This ScannerDanner video goes into restricted exhaust testing in depth: