Rough Idle in gear/ Hard shifts into gear/Poor idle RPM

[Hoffer00]

Start the car with hood open. Then push done on the spark plug wires listen for the tick to go away. Check all 4. If the ticking continues then change the oil good recommended oil like Rotola T or mobil one. If the ticking is still there it's not your lifters.

[Cold Dark Shadow]

if its not the lifters what would it be?
The sound is coming from under the valve cover