Ex telling kids bad things about me

We do not have a custody/consent order. Is there any recourse for my ex telling the kids bad things about me in an attempt to alienate them from me?

Without an order in place, there is really nothing you can do about it. If you file suit and put on evidence of the disparaging remarks, the judge will take this into consideration when making a determination about custody and it will not bode well for the party making the negative comments to the children.