In reading some of the posts regarding TFI function there has been some discussion about the computer running in open loop because of the o2 sensor resistor. The question I have is what is the difference in the AFR in open loop as oppossed to closed loop. I have heard before that untill an engine reaches running temp the control is set to an open loop to keep from setting codes and that open loop is a rich mixture? This I learned about fuel injection in cars, not sure if it is the same for this application. I think this is the correst spot to post this, right Hoople? Harley.