My car is sick (+25% LTFT)...with Datalog! Any Datalog experts please?

[InFiD3ViL]

UPDATE!
My car has now been healed!

DynoSteve and some of you other guys were correct. I replaced both B1S1 and B2S1 with the OEM Denso sensors and now my trims are going back to normal and I am getting good voltage from B2S1, not 0 - .05v like I was when it was running like garbage.

Thanks again for all the input!




So my SS is running like garbage. I am getting around 14 mpg, random stall on tip-in (From stop only), up/down idle - especially at cold start (550 rpm - down to 300 rpm - cycles), LTFTs pegged at +25%. Rough idle is much worse during cold start.

Once warmed up it runs a bit better. On heavy pulls she seems to run great.

I sent a Datalog to DynoSteve and he recommended changing out the Bank 2 Sensor 1 O2. He is my tuner and of course the B1S2 and B2S2 are tuned out due to my long tubes. Thing is, I know he is very busy and I am not sure he had much time to really go through it.

I am by no means an expert, so I am not sure if I am barking up the wrong tree here, but I have been focusing on the voltage for my B1S1 and B2S1. At most times while running a live log, or using the Torque and Dash Command app via bluetooth I am getting 0 volts to both sensors, except during decel where bank 1 will jump up a little bit.

What has me confused is that even though the Sensor # 2 O2s are turned off, I am still getting .455 volts reported from both of them using Dash Command and Torque apps.

I am sure that DynoSteve is pointing me in the right direction, but I am seriously broke right now and can't just throw parts at it until I know what's up for certain. I don't have access to a multitester just yet, but I get paid Thursday and plan on testing various sensors. I pulled out all of my spark plugs and they were absolutely covered in soot. I cleaned them all and checked the gap. DynoSteve said that this is normal and he would be worried if they weren't covered in soot? I am not sure if this is a symptom or cause of the issue. Possibly fouled beyond cleaning?

I am attaching a datalog to this thread if anyone would be so kind as to take a look for me. Sorry for the extra PIDS, as I wasn't sure what to add/not add and there may be a few duplicates. Ran for 15 mins, about 3 mins at idle including various driving states with one nice pull to 6K rpm.

I am NOT getting any check engine lights or codes thrown! This is what is the most frustrating, as I see some of you get codes if you sneeze near your car.

Mods are in sig

I made the following thread 1 week ago, before the poor idle and stalling started. I am certain it's related to this: http://www.camaro5.com/forums/showthread.php?t=494895

Thank you for your time!

• No recent changes to car or tune
• I do around 120 miles per day, so empty fuel tank every 2 days
• Switched up gas stations AFTER issue started. Usually use Shell 93, last tank was Mobil 93. ALWAYS run 93 octane.
• Checked wiring on both O2s, checked to make sure tightened down as well
• Cleaned MAF with MAF cleaner
• Cleaned Air Filter
• Checked for vacuum leaks and unmetered air
• Checked for exhaust leaks
• Datalog shows a gradually falling reading on both Bank 1/Bank 2 #1 sensors for voltage, but barely reads a value for B2S1 - Low voltage -Not sure if side effect of the lean condition
• Did a battery pull after the Datalog to clear all learned values. Within 70 miles, was back to +25% LTFT on both banks.
• Removed and cleaned heavily sooted spark plugs. DynoSteve said this amount of soot is normal?
• Average Fuel pressure is around 58psi
• Put my OEM, non-locking fuel cap back on
  

DATALOG attached below

[Iron Lung Jimmy]

OK... total shot in the dark, but free and easy... disconnect the VTC.

[JerTM]

Bank 2 sensor 1 is not shut off by your tune. Bank 2 sensor 2 and bank 1 sensor 2 are. Sensor 1 is always upstream of the cat and has direct affect on fuel trim. Sensor 2 is behind the cat and has zero input for fuel trim, it ONLY monitors catalyst efficiency, nothing more. Trust him and replace the B2S1. You shouldn't see a square wave in ANY O2 reading regardless of position.

[InFiD3ViL]

Originally Posted by Iron Lung Jimmy

OK... total shot in the dark, but free and easy... disconnect the VTC.

lol, that was my next move, just to eliminate the possibility. I'm aware of the issues others have had with them, usually out of nowhere. But most times it is accompanied by some sort of code being thrown.

Could that cause the fuel trims to go wacky?

[JerTM]

Originally Posted by InFiD3ViL

lol, that was my next move, just to eliminate the possibility. I'm aware of the issues others have had with them, usually out of nowhere. But most times it is accompanied by some sort of code being thrown.

Could that cause the fuel trims to go wacky?

Not likely. The ecm does take in to account the​ throttle position , but fuel trim relies more on maf readings and O2 readings which a "quicker" throttle opening will show up in the maf.

[InFiD3ViL]

Originally Posted by JerTM

Bank 2 sensor 1 is not shut off by your tune. Bank 2 sensor 2 and bank 1 sensor 2 are. Sensor 1 is always upstream of the cat and has direct affect on fuel trim. Sensor 2 is behind the cat and has zero input for fuel trim, it ONLY monitors catalyst efficiency, nothing more. Trust him and replace the B2S1. You shouldn't see a square wave in ANY O2 reading regardless of position.

Just confirmed it's not the VTC - no difference after removing it and battery pull. Not that I thought it would, but it's good to scratch that off the list.

I am going to replace the sensor, no doubt. Should I put a set of fresh plugs in too? They were absolutely covered in carbon soot. I cleaned them off pretty good, but the ceramic insulators are no longer white, now a dull gray. Just want to make sure they aren't fouled now. Also wondering if it is better to replace the pre-O2s in pairs or is that just throwing money away? I am going to replace with the OEM ACDelco Part #12617332

[davidscamaro]

I know quite a bit about data logging, dyno steve is correct and you will need to change out your upstream O2 sensor. You only need to change the dead one but it has to be the same brand and make as it's mate. Your car being a 2010 will need a denso brand (will come in a ac delco box)

[InFiD3ViL]

Originally Posted by davidscamaro

I know quite a bit about data logging, dyno steve is correct and you will need to change out your upstream O2 sensor. You only need to change the dead one but it has to be the same brand and make as it's mate. Your car being a 2010 will need a denso brand (will come in a ac delco box)

Alright man, thank you very much!

I can't wait until this is over.

[DJ_BigC]

If both banks 1 and 2 are reading +25% your car is currently running lean beyond a calibrated threshold. From my experience it's most likely not the one oxygen sensor thats going to fix that if both banks are at +25 and i highly doubt that both sensors have failed at the same time, our vehicles are pretty smart, your car is seeing an excess amount of unmetered air enter inside your engine causing your pre cat sensors to compensate the fuel trim as much as they can to make the car run okay ish by adding fuel until it runs stable at roughly +25.

If both banks are reading the same, this is something that affects both banks and is not necessarily side specific. Most commonly for equal readings for both banks i've seen cracked/rubbed through/incorrectly installed PCV lines, a faulty EVAP purge solenoid or malfunctioning EVAP system, faulty fuel composition readings/sensors, weak or failing fuel pumps, faulty MAF Sensors, damaged/kinked/crushed/improperly fastened cold air intakes tubes. Certain things that were more side specific were bad intake gaskets or gasket, exhaust leaks are the manifold to head flange, misfires due to bad ignition components or a fuel related issue that can be isolated to one bank or cylinder... I'm sure there's a few more things in each category i just can't think of them all currently. It's defenitly not your VTC, buti wouldn't count it out.. if you need additional information feel free to PM me.

[InFiD3ViL]

I appreciate all the help guys.

I will update as soon as I get this figured out.

Thanks again!

[InFiD3ViL]

My car has now been healed!

DynoSteve and some of you other guys were correct. I replaced both B1S1 and B2S1 with the OEM Denso sensors and now my trims are going back to normal and I am getting good voltage from B2S1, not 0 - .05v like I was when it was running like garbage.

Thanks again for all the input!