2005 Ford Mustang GT engine/spark knock?

It seems to have a engine/spark knock at idle. I can take off and it drives fine. Oil pressure gauge is normal. Car just had a fresh oil change and air filter change. Oil is motorcraft 5W20. Car has 111k miles on it. If I turn the car off, and turn it back on the knock goes away. No check engine light is coming on. Any help will be appreciated

Check engine light is only in case the emissions control system is giving a code. Other issues can still have a code but not trigger the check engine lamp. You need to get the codes read from the OBD2 port regardless.