2010 Camaro ls3 in s10 stft an o2 readings

[Jshaffer123321]

Just swapped a 2010 ls3 into my s10 blazer I got it running today but stft is all over like -18 to +2 and o2 readings are all over from 30 to 900mv I'm new to all this figured the factory tune would be somewhat close but I'm afraid it wasnt that easy

[Jshaffer123321]

Also I have everything connected other then rear o2 sensors and deleted everything for transmission..

Everythings original to engine other then stainless works headers and cai.

[5FDP]

Oxygen sensors like these, called narrowbands are designed to switch back and forth where the middle is 450mv. So seeing it bounce between 50 and 900mv all the time is normal.

If your short term trims are super bouncy and your long term trims are either really positive or really negative you may have some issues to look into.

Verify you have zero vacuum leaks, no exhaust leaks and that the exhaust is complete. No dumped exhaust within 20inches or so of the primary upstream o2 sensors. Verify you have proper fuel pressure of 58psi.

Headers will require some tuning, the stock calibration can not account for this.

The MAF sensor needs to be in a straight piece of tubing and it needs to be in the stock size piping. Larger or smaller piping will throw everything off.

Get yourself a wideband o2 sensor as well, you'll need one for tuning.

[Jshaffer123321]

Yes the intake is 4 inch I do not have factory intake to compare

Also I have no ltft readings they stay at zero

As for exhaust they are not even close to 20 inches I have open headers at the moment I should have exhaust done in a couple of weeks.

Fuel pressure is running 62psi and i have zero vacuum leaks from what I can tell.

[5FDP]

Yeah, then anything you see with the oxygen sensors is useless.

The incomplete exhaust is sucking in air and skewing the sensors and the larger intake tubing will be throwing the fueling off some.

The LTFT likely won't do anything until you get it completely warm with full exhaust and they will start reporting once the engine enters closed loop fuel control.


If all you are trying to do it just let it run and idle, that is fine. Can't do anything else until everything is finished up, then on to wideband tuning.

[Jshaffer123321]

Okay so today I put the exhaust on it, started it up and it goes 450mv for a few then slowly drops and stopped and sat at 8mv stft spiked to the 20 range then shot to 0 and o2s read 8mv car had no power I couldnt even rev it up to see if it would change anything

[5ft24]

Make sure the O2 sensors aren't hosed. Sometimes welding the exhaust, if they ground the welder to the frame or body instead of where they are doing the welding can toast the O2's.