2002 SOHC idle issue
So have a 2002 2.0L SOHC split port that will not idle properly. It is a new engine, runs like a top until it comes down to the low idle then it begins to stumble but not a miss more like and idle serge up down up down but not erratically. I have checked for the normal things like the elbow in the PCV hose, put in new plugs and wires, tried a different coil pack, changed the idle air control and TP sensor, checked for vacuum leaks and wire connections, I have no codes.
The engine is new thanks to a valve seat, but I am having troubles with this and thought perhaps I have overlooked something, any ideas