I have a case of misfires on cyl 1 only on idle. While cruising around or even at WOT, no misfires nor loss of power. Plugs and coil packs are good. Did a compression test and cylinder 1-2 was a bit lower than 3-4.

Test was looking like that from 1 to 4: 120-130-160-150

Did a leak down test too and results are from 1 to 4: 40%-20%-0%-10%

From the noise, it sounds like valves but I'm not sure. I used a snake camera to check the intake valve and inside the cylinders itself and everything was looking fine. Wasn't able to check exhaust valves tho. I bought a bottle of upper engine and fuel injectors cleaner and will pour it slowly by the vacuum tank hose on top of the intake to begin with and see if it improves something or does nothing at all.

My question is: Can a bad valve seal or even a bent/crooked valve cause my issues? Or I should check somewhere else?

 

How clean are the intake valves? You should be able to feel misfires if they are so dirty that they cause misfires.

Very common issue and can result in lower compression due to sealing issues around the valve.

 

When you did the leak down, you should have determined where the air was leaking from. Air from the intake port is intake valve, air from exhaust port is exhaust valve, air from crankcase is ring sealing, air in coolant system is head gasket, etc. You may want to do a deep dive with Cyl 1 again here to find out if it is a valve.