Thread: Valve cover breather

does this wreck havoc with the wideband? mine seems to bouncing all over the place from 14-17

It allows unmetered air into the motor. if your not intercooled take it off. And even if you are I would try to set up a catch can set up to get rid of the vacum leak

Breathers are only needed if the cars PCV system is no longer there.

And the WB should only be bouncing from 14-16 while at idle and crusing as its trying to stay as close as it can to stoich.

Turbo cars require the breather or an air pump. You cannot have a PCV system with the inlet after the turbo because the turbo will pressurize your crankcase and destroy seals, so the breather becomes the inlet. If you still have your PCV valve functioning, the air coming in from the breather will circulate back into the cylinders after the MAF, so will add air to the mix that the tune does not know about. It is very little air, and does not create any problems. The fluctuation of AFR from 14 to 17 is because of closed-loop, not because of the extra air. If you want your wideband to read steady at idle and cruise, you would have to switch to an open loop tune, but it is not necessary. Closed loop works fine. Just make sure to tune correctly for part-throttle as well as full throttle.