STFT and Misfire Codes

[SteveWK]

Hello All,

I hope you don't mind me posting this here instead of the 2013 GT500 forum. It is ECU related though.

I have a 2013 GT500 and several months ago I removed the longtube headers and put the stock exhaust back on. Since then I have been getting random misfire code P0300 and hard misfires on a variety of cylinders P030X. I have been data logging trying to figure out what the problem is instead of throwing parts at it. Tonight I noticed while the CEL light is flashing during misfire both bank1 and bank2 STFT peg at 0% and return to normal operation when the misfire clears. The STFT remain at zero even when I give it throttle while the CEL light is flashing.

I have performed a crank relearn and loaded the stock tune. Neither made a difference. Also, tomorrow I will be checking to see if the left and right O2 sensors are plugged into the right side. I didn't do the exhaust work.

Is this something the ECU does when certain variables are exceeded or does this point to a problem with my O2 sensors?

Thanks for your input.

Steve

 

[silver_cobra_01]

I very well could be wrong as I'm still learning, and learning on a much older car at that, but I believe it is probably going from closed loop to open loop when you see the STFT's peg at 0%. You should be able to datalog fuel source to confirm, if you aren't already.

I know that isn't much to go on, but hopefully someone more experienced can chime in.