Engine Knock/Rough Idle (2021 CX-5)

Hi Folks,

I had the repair done to my 2021 CX-5 Signature to replace the faulty exhaust valve seals which was causing excessive oil burn. Since the repair was done I've noticed the following:

1) On cold startup, (after initial RPM spike has come down) I am hearing what seems to be a knocking sound, almost like the sound of a diesel engine but to a lesser extent. It's not the ticking sound that is normal for the Skyactiv engine, but a knocking sound. It's not super loud, but noticeable to my "car guy" trained ear and I don't remember hearing it before the exhaust valve seal repair was done.

2) The idling seems to be more rough, even when the engine is warm. I can see the engine cover vibrating while idling (not sure if this is normal), even when the AC is turned off. I can also slightly feel the vibration of the idle in the cabin. It's mild, but I can feel it. I don't remember this before either.

I know they had to take apart a lot of the engine to do this fix so I'm second guessing if it was put back together to spec. I don't notice any abnormal sounds or feeling when the car is moving under throttle, just while idling.

I am wondering if the engine knock and rough idle are due to the exhaust valve seal repair reassembly, or if it's something else? I have run a bottle of Redline fuel injector cleaner and a bottle of Techron fuel injector cleaner since noticing the knock and rough idle but it didn't improve anything so it's most likely not clogged fuel injectors. The car only has 25k miles on it.
Some of the symptoms you described sound like a motor mount that wasn't torqued correctly, however the stem seal procedure doesn't call for any of the mounts to be touched.

Are you thinking about DIY diagnosis, before taking it back to Mazda?
Thanks for the information! I am going to take it back to Mazda. I also notice when I am backing out of my driveway when I reach the street before putting into drive that the RPMs tend to drop really low and I feel the low idle vibration. I'm not sure if it's a timing issue that could have been messed up with the repair, fouled spark plugs due to the oil leak problem from the faulty exhaust valves, fuel filter, fuel pump, fuel regulator....so many possible reasons (I Googled these) :). But the knocking sound at cold start up is separate from the rough idle. I guess the best thing to do is just take it in and have them hook it up to the computer for any fault codes and maybe do an engine noise test (if there is such a thing).
Could be lifter noises in your case.
Could you post an audio file here?

Engine mount issue is different.
You can see engine moves more violently by revving the engine with gear in N or P and hood open. (someone does the revving)
If you accelerate or brake, you hear a clunk ... that is engine mount issue.