Po171 System to Lean Bank 1

[shitstang01]

Just replaced both 02 Sensors yesterday car finally seems to be reading but not maybe adjusting for some reason. I started noticing when I brake or begin to come to a stop (braking) or sometimes even randomly driving my AFR surges between 17-20 for a decent amount of time ..is this normal ?
I cleared the code drove it a bit and it came back on as I previously had codes on the car when my sensors were bad. I checked under the engine bay all hoses/clamps are tight. I also reloaded my tune. The o2 sensors are screwed in tight and angled perfectly as well..not sure what else to do or why the car isn’t adjusting.

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[svtfever]

Reset KAM. Then what do STFT read on both banks. What does LAMDA read?

 

[shitstang01]

Reset KAM. Then what do STFT read on both banks. What does LAMDA read?

How do I reset KAM? & what is STFT?

 

[svtfever]

Do you have a handheld tuner? STFT is short term fuel trim. Select STFT and LAMBDA PIDs and see what they say

 

[svtfever]

You you don’t have handheld tuner. Just unplug battery for a while and let car reset

 

[shitstang01]

I hav

You you don’t have handheld tuner. Just unplug battery for a while and let car reset

I have a nGauge

 

[ugstang17]

Just replaced both 02 Sensors yesterday car finally seems to be reading but not maybe adjusting for some reason. I started noticing when I brake or begin to come to a stop (braking) or sometimes even randomly driving my AFR surges between 17-20 for a decent amount of time ..is this normal ?
I cleared the code drove it a bit and it came back on as I previously had codes on the car when my sensors were bad. I checked under the engine bay all hoses/clamps are tight. I also reloaded my tune. The o2 sensors are screwed in tight and angled perfectly as well..not sure what else to do or why the car isn’t adjusting.

AFR on the dash will go to 20.0 when the car is in a form of "engine braking mode" for no better term. This will occur when you let off of the throttle and coast for a period of time. Under common throttle 14.0 shoudl be seen. at WOT the number will be lower (12.8 on NA setups and 11.7 or richer on FI setups commonly). Some tuners like PBD will disable this in their tuning process. I prefer it on personally so I always make sure my tuner complies with that.

Without more details on the setup and what led to your issue there is no crystal ball capable of providing an accurate guess as to you problem. Many things can cause that code. Bad cable, O2 sensor connectors get swapped (common on the S197 setups when guys would add LT's or swap out to an OR pipe) broken wiring etc. Why they were needing replaced to begin with would be as important to solving the problem as anything.

Vague questions produce Vague guesses to the resolve.

STFT = Short term fuel trims. Go do some research to learn about it or read Greg Banishs book Engine Management - Advanced Tuning.

 

[shitstang01]

AFR on the dash will go to 20.0 when the car is in a form of "engine braking mode" for no better term. This will occur when you let off of the throttle and coast for a period of time. Under common throttle 14.0 shoudl be seen. at WOT the number will be lower (12.8 on NA setups and 11.7 or richer on FI setups commonly). Some tuners like PBD will disable this in their tuning process. I prefer it on personally so I always make sure my tuner complies with that.

Without more details on the setup and what led to your issue there is no crystal ball capable of providing an accurate guess as to you problem. Many things can cause that code. Bad cable, O2 sensor connectors get swapped (common on the S197 setups when guys would add LT's or swap out to an OR pipe) broken wiring etc. Why they were needing replaced to begin with would be as important to solving the problem as anything.

Vague questions produce Vague guesses to the resolve.

STFT = Short term fuel trims. Go do some research to learn about it or read Greg Banishs book Engine Management - Advanced Tuning.

Ok thanks. Had to replace both o2 sensors due to running open headers for 2 months I believe the heat was a factor and the wiring got messed up.

 

[shitstang01]

Reset KAM. Then what do STFT read on both banks. What does LAMDA read?

STFT bank 1 is between 15-20% & STFT bank 2 is fluctuating between -3 & 1.

 

[svtfever]

Bank 1 is very lean. Do the numbers DEcrease when under load. Check for exhaust leaks on passenger side.

 

[shitstang01]

Bank 1 is very lean. Do the numbers DEcrease when under load. Check for exhaust leaks on passenger side.

I went to get my oil changed the other day and I have an exhaust leak from one of the bolts came out on the passenger side of my headers, I didn’t pay it any mind because they said it wouldn’t affect performance but I can hear it when driving it’s like an air and rasp sound coming from that area when accelerating. Could this be the reason why ?

 

[svtfever]

Yes. That could be it. Vacuum leaks will play bad with fuel trims if it’s post MAF. Exhaust leaks will do the same because it is pre- o2 sensor. It’s unmetered air. The car will correct it self by adding fuel but you need to make sure it’s tightened back up. If you leave it like it is you may see STFT drop but you will see LTFT, long term fuel trim, increase. Make sure it’s tightened up and you should be fine.

 

[shitstang01]

Yes. That could be it. Vacuum leaks will play bad with fuel trims if it’s post MAF. Exhaust leaks will do the same because it is pre- o2 sensor. It’s unmetered air. The car will correct it self by adding fuel but you need to make sure it’s tightened back up. If you leave it like it is you may see STFT drop but you will see LTFT, long term fuel trim, increase. Make sure it’s tightened up and you should be fine.

Ok great thanks for the info !

 

[ugstang17]

This is a good read. Its the basics of reading LTFT's and what they may indicate.

http://iihs.net/fsm/?d=8&f=Adaptive Fuel DTC Diagnostic Techniques.pdf&p=1

Your problem appears to be back 1 (passenger side related). Bank 2 is fine. As mentioned look at the LTFT's. Note how they are reacting. Then look at the attachment from the Ford tech manuals I am providing and see which applies. You already know that the problem resides on bank 1. The exhaust leak you mention will cause false reads and STFT's to go nuts. Resolve that and then revisit STFT's and LTFT's. BTW LTFT is Long Term Fuel Trims. That is what changes (if active in the tune) to correct for STFT's that remain out of a specified range for a given period of time. Once they exceed a certain amount they gen a CEL as well if my theory is accurate. Haven't used it in a while.

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