When starting up my car after sitting for a while, I hear a strange tapping noise only at warmup and then it goes away.

I'll hear duh guh duh guh then no tapping then duh guh duh guh duh guh until it goes away after a few seconds. Are my valves sticking?

After warmup there is no other tapping noises.

 

It's likely your valves, a lot of Hondas are known for this. They don't seat properly when cold, and by the time the engine heats up and metals expand, it goes away.

If it's really bad a valve adjustment can help a little bit

 

If it is a DOHC VTEC motor, it may be the LMA's (Lost Motion Assemblies) It is a common problem found in these motors.

 

Thanks for that. It sounds like the valves are being hit from the bottom and top if they are sticking or not seating properly. There are some additives that might help. I just completed a valve adjustment and it's a relatively quiet engine after warmup.

 

yeah, my sohc engine has that problem as well. Only in the winter though.