AFR's off between banks HELP!
 

I have a situation with my AFR's and was hoping I could some thoughts on what the issue might be. I did some data logging last night and found that bank 1 is running almost 1 point leaner than bank 2 under WOT. And when engine braking, bank 1 goes to around 20 while bank 2 goes full lean. I assume this has been going on for some time but have no idea how long. The car hasn't been acting weird in any way other than throwing a P2A00 code which I cleared and hasn't come back. I'm hoping there is no risk of motor damage from this. Attached is a data log showing the problem. It starts out cruising, then goes to WOT, then ends with engine braking (foot off the gas & coasting).

there is a few possibilities on this such as;

- looser bolt on the headers/cats/testpipe flange which create a leak ( I had this problem 2 years ago.)
- I suggest you to switch those AFR sensor in the opposite bank to see if the problem still remain the same or if the AFR will change by installing the sensor into the other bank.
-IF the sensor appear to be alright from doing what I suggest , its to try to do the same with the MAF sensor
-If nothing work and its always the same, tune your Cylinder compensation with Uprev

I have the whole Bank#2 setup 1.5% more than Bank#1 which gives me the same AFR on both bank.

Thanks for the info! I'm going to swap the sensors when I get home after work. I have the F.I LTH's and F.I. CBE and had/have a small leak where the CBE meets the LTH. The sensors are mounted right by there, so it may be the leak.

When you had the leak, did it do the same thing? (AFR's running leaner during WOT & going richer during engine braking)

I don't recall anything like this..

I just look at your datalog since I couldn't from work today and to be honest, I have no idea what's going on.


Let us know what happen when you switch the sensor from bank to bank...

UPDATE: After some more data logging, my buddy and I noticed that the voltage on the bank 1 sensor (at full lean) was peaking at 3 volts while Bank 2 was peaking at 5 volts. Since I have the F.I. LTH's, I had to extend the 02 sensors. To narrow down the problem, I replaced and re-soldered the bank 1 sensor extender and swapped the sensors over (bank 1 to bank 2 and vice versa) The result was that the problem moved from Bank 1 to Bank 2 which, I can only assume, means that the problem is the sensor itself. I am ordering another sensor and hopefully this issue will be solved. Has anyone heard of a brand new sensor doing this?

didn't know you had the sensor wire harness extended for the headers...
we have seen this problem at a few occasion here on the forum.

re-soldering the wire properly or getting new one as always solved the problem from what I have seen.
atleast you know where there problem is now ;)

Does anyone know if driving like this can hurt my engine in any way?

not if you don't abuse the car.
but I would recommend getting the problem fixed asap.

Yea, I'm ordering the 02 sensor today and I've been taking it easy on the car since I found this problem. However, I've been driving it hard before then and dont know how long this problem has been there. Since I switched the sensors and the problem moved to the other bank, then Its obviously something to do with the sensor/wire/connector. I just worry that because its taking these bad readings, the ECM will try to compensate and end up hurting the motor. My main concern is when I let off the gas (engine brake) and one bank goes to 30 AFR and the other bank is in the 20's. My injector pulses stay the same, so I assume its not adding any fuel, but I dont really know how all that works.

UPDATE: I replaced the AF sensor (front 02 sensor) and all is well :) Hopefully no damage was done from driving with a bad AF sensor for the past few months.