Nissan 370Z Forum - View Single Post - O2 and A/F Sensor Readings

fitxpert · 06-24-2014, 11:17 PM

Hi guys,
I'm posting here in the hopes some of you can help me out.

Car sporadically bogs on acceleration. This gets worse as the car gets warm. Usually it's out of first gear. She's fallen on her face plenty of times at a stop light. Also, accelerating will sometimes have a 2-3 second pause and then sudden acceleration once revs get to 2500+ rpm. Gas mileage has gotten worse by about 2 miles per gallon. The car is not throwing any codes, although through Torque, I did receive a "pending P0420" twice, but neither stuck.

I've cleaned the MAF sensors, cleaned the fuel system with Redline SL1, changed out the air filters, and seen minimal results.

Here's where I'd love your expertise. I have a good friend who is a tech, and he was generous enough to bring a Snap-on OBD Scan tool. We hooked it up, warmed up the car and took some snapshots of what the A/F and O2 sensors are doing. The dealership did the same thing and told me they can't move further because everything is "within spec." I was able to set up Torque so the same sensors are displayed and I took a screenshot.

At idle, we noticed the bank 1 sensor 1 (AF Sensor) undulates up and down (similar to a sine wave), whereas the bank 2 sensor 1 stays pretty flat. What could be causing this? My understanding of AF sensors is that they should remain relatively flat. Secondly the bank 1 sensor 2 (post cat 02 sensor) mimics bank 1 sensor 1 with what looks like a sine wave. Bank 2 sensor 2 tries to stay flat, but sometimes tapers off slowly or drops fast and then rises again. What the heck is going on? I'm primarily interested in Bank 1 Sensor 1. Is the undulation normal? and if not, what could be causing it to do this?

I checked the fuel trims too - Bank 1 undulates and Bank 2 looks like it's relatively steady at idle. What causes the undulation? I'd like to get my gas mileage back to what it was.

Thanks for the input guys.

Sensor Screenshot

06-24-2014, 11:17 PM	#1 (permalink)
fitxpert Base Member Join Date: Sep 2013 Location: Tempe, AZ Posts: 34 Drives: 09 370Z White MT TRG Rep Power: 12	O2 and A/F Sensor Readings - I need an armchair diagnosis! HELP! Hi guys, I'm posting here in the hopes some of you can help me out. Car sporadically bogs on acceleration. This gets worse as the car gets warm. Usually it's out of first gear. She's fallen on her face plenty of times at a stop light. Also, accelerating will sometimes have a 2-3 second pause and then sudden acceleration once revs get to 2500+ rpm. Gas mileage has gotten worse by about 2 miles per gallon. The car is not throwing any codes, although through Torque, I did receive a "pending P0420" twice, but neither stuck. I've cleaned the MAF sensors, cleaned the fuel system with Redline SL1, changed out the air filters, and seen minimal results. Here's where I'd love your expertise. I have a good friend who is a tech, and he was generous enough to bring a Snap-on OBD Scan tool. We hooked it up, warmed up the car and took some snapshots of what the A/F and O2 sensors are doing. The dealership did the same thing and told me they can't move further because everything is "within spec." I was able to set up Torque so the same sensors are displayed and I took a screenshot. At idle, we noticed the bank 1 sensor 1 (AF Sensor) undulates up and down (similar to a sine wave), whereas the bank 2 sensor 1 stays pretty flat. What could be causing this? My understanding of AF sensors is that they should remain relatively flat. Secondly the bank 1 sensor 2 (post cat 02 sensor) mimics bank 1 sensor 1 with what looks like a sine wave. Bank 2 sensor 2 tries to stay flat, but sometimes tapers off slowly or drops fast and then rises again. What the heck is going on? I'm primarily interested in Bank 1 Sensor 1. Is the undulation normal? and if not, what could be causing it to do this? I checked the fuel trims too - Bank 1 undulates and Bank 2 looks like it's relatively steady at idle. What causes the undulation? I'd like to get my gas mileage back to what it was. Thanks for the input guys. Sensor Screenshot Last edited by fitxpert; 06-24-2014 at 11:22 PM.