Mass Air Flow Sensor Voltage

[Rebar 911]

Been a while since I looked at this, so hopefully I explain correctly: There are 3 o2 sensors on each bank for this car: Pre-cat, mid-cat, and post-cat. The pre-cat sensor is used for fuel trim control, which should be sensor 1. See if you can find sensor voltage on the GAP tool for sensor 1, and then watch it or graph it using the graph button on the GAP tool - the voltage should move smoothly between about 0.1 and 0.9 v, back and forth like a wave.

I believe the mid and post-cat sensors are for emissions and cat converter health monitoring. I think only one of these two have a value on the GAP tool (sensor 2), and it stays pretty steady around 0.5-0.7v if I remember correctly.

Here is the sensor graph.

The other thing I’ll mention - your fuel trims are off, but not way off. I’m not actually sure they’re off enough to cause any drivability issues. Still worth checking your o2 sensors, but I’m wondering if what you are feeling at 40 - 50 mph (1600-2000 rpm) is engine roughness (i.e., misfire) or some other vibration. Is it when you hold the throttle steady or when accelerating (or both)? Then it smooths out past that point? Does it do it both in sport mode and regular drive mode?

It's when I hold the throttle steady and it tends to settle down when it's in sport mode. Regular mode is when it's really noticeable but not noticeable to the passenger but really to me the driver. And thanks again for all your help here

 

[jlglr4]

Graph says sensor 2. For fuel control, need to be looking at sensor 1. warm engine, just idling (don’t throttle).

For this sensor 2 data, was the engine just idling? I wouldn’t have expected so much variation. If I get a chance today, I’ll try to run the test on my car for comparison.

 

[Rebar 911]

Graph says sensor 2. For fuel control, need to be looking at sensor 1. warm engine, just idling (don’t throttle).

For this sensor 2 data, was the engine just idling? I wouldn’t have expected so much variation. If I get a chance today, I’ll try to run the test on my car for comparison.

I was driving

 

[Rebar 911]

Graph says sensor 2. For fuel control, need to be looking at sensor 1. warm engine, just idling (don’t throttle).

For this sensor 2 data, was the engine just idling? I wouldn’t have expected so much variation. If I get a chance today, I’ll try to run the test on my car for comparison.

I don't have a value for voltage for sensor 1. I have other values for sensor one. Should I try something different?

 

[jlglr4]

I think it might be listed as lambda. I’m attaching some old data I had once posted here in the forums. You can see the oscillation to look for in working sensors.

 

[Rebar 911]

I think it might be listed as lambda. I’m attaching some old data I had once posted here in the forums. You can see the oscillation to look for in working sensors.

Here is sensor two again this time at idling

 

[Rebar 911]

Lamda sensor idling

 

[jlglr4]

hmmm…tough to read that graph of sensor 1. Try to compress the x axis timescale so we can see more time - like maybe 80-90 seconds or so at least. And expand the y axis so you can see the fluctuations better. You should be able to use your existing read and just pinch or expand with your fingers in the graph area.

you can clearly see sensor 2 bank 2 dropping periodically.

 

[Rebar 911]

Here we are with a 90s time frame. Idling after about 30m of driving.

 

[Rebar 911]

hmmm…tough to read that graph of sensor 1. Try to compress the x axis timescale so we can see more time - like maybe 80-90 seconds or so at least. And expand the y axis so you can see the fluctuations better. You should be able to use your existing read and just pinch or expand with your fingers in the graph area.

you can clearly see sensor 2 bank 2 dropping periodically.

Additional updates. I was driving it last night and observing the bounce when driving 70mph steady at 1500rpm in regular mode. I shifted to sport mode and same thing. Then I started manually changing gears and found things settling down in s4 - s6 with no hesitation or bouncing. Wondering if this adds any more ideas? Am I wrong to order some aftermarkets O2 sensors and at least start there?

Clueless here and really appreciate the help.