What is the difference between o2 sensor closed loop and open loop. In TuneEcu the icon is greyed out so am assuming it is a closed loop. Any help please.
I don't know about tuneecu.
Closed loop running is where the ECU monitors the O2 sensor and changes the air / fuel ratio to try to keep the O2 level at a specific value. This can cause some hunting as the mixture can be constantly changing. Open loop running ignores the O2 sensor.
The ECU only tries to apply closed loop when the target A/F ratio is in a specific range - around 14.5:1 by weight. So you can either change the map so it's never in that range (which I did with my '04 to eliminate surging) or more crudely by fitting an O2 sensor eliminator which tells the ECU that all is fine & dandy.
Iansoady
When you say changed the map did you go above this point or below this point?
Made it richer ie lower numbers. I kept it below 14.0.
12.5 to 13.5 is good, anything below 12.5 is going to use noticeably more fuel. 12.0 makes good power but uses fuel and runs harsh. Anything below 12 is too rich.