The for the past couple months I’ve been getting this random misfire usually at stoplight fully warmed up. It started as a single to couple misfire almost felt like someone hitting my car. Putting the car in neutral to take some load off the engine seems to help a little but tonight it was really bad. The car drives complete fi e it’s just once it goes below 1k rpm that it misfires and can’t idle properly. My check engine light is on for my cats but the car won’t give me any misfire codes. I just rebuilt the motor so compression should be fine and plugs are only 40k miles old.

 

Well I think I found my problem. I scanned the car and got p0404 EGR valve performance. I pulled the egr valve off and there was a piece of cat material lodged in the valve holding it open.