When I hook up an OBD2 reader to log data, I notice if I sit in traffic for a while, the car idles fine, but the OBD2 scanner sometimes shows 11,000+ rpm unless I blip the throttle. Is that the crank sensor acting up? Can a dirty ground cause that?

 

For anyone reading this, yes a dirty ground will cause issues. I remember I had spilled some oil topping up, and some got on the ground behind the head. Hit it with some contact cleaner and it's fine now.

 

May be a loose bolt

 

I checked, it was tight but it was covered in oil too.