Thread: super lean and rich conditions at idle after ECU swap

So I have a Calum basic ecu with a SAFC II and I swapped the setup with another tuned ecu for my setup. I reconnected the MAF sensor (orange) wire. SAFCII is now removed

The new ecu starts up the car, but idle runs very lean around 16:1. Trying to keep the car alive, bumping the throttle made AFR's very rich around 12.5:1. Car idles ok, but rich, but then drops back to extreme lean after a few seconds.

What would cause such an AFR issue at idle just by swapping ECU's? Fuel pressure? new ECU not tuned right? Is it adjusting to the different motor? other SAFC II wires getting in the way?

any ideas will help. Thanks

Did you mess with the TPS or idle adjustment screw?

Nothing was played with. Just the swap of the ecu and removal of the SAFC II.

Ok, it sounds like it was possibily tuned for modifications you don't have/didn't want

Most likely the tune you have is a base tune to get you running. You need to have the new ECU tuned for your car.