Honda Accord 2007 what's going on?

I have a 2007 Honda Accord 2.4 (SULEV)

#1 On a cold start I can clearly hear the car misfiring for the first 20 or so seconds until it starts to get a little bit warm (although it never throws any misfire codes)

#2 I hear a knocking or pinging sound that mostly goes away after the car gets to operating temperature (but not completely)

#3 It just feels slow and lacks power especially going uphill

I don't have a smoke machine to test for vacuum leaks and don't want to take the manifold apart unless I have to…

Added (1). Yes, I recently changes the spark plugs and it made no difference

Could be a broken flywheel.

You need to have the valve adjusted. This is the procedure for a valve clearance check/adjustment on the 4cyl. 7th generation i.e. 2003 - 2007 Honda Accord. As per the owners manual, this procedure is recommended every 110,000 miles or if the valves become noisy. Intake valves are responsible for letting the air-fuel mix into the combustion chambers whilst the exhaust valves vent the burnt gases into the exhaust system. It's widely said that exhaust valves tighten while the intake ones loosen over time (for solid valves though). The valve clearance for this model is:

Intake: 0.21mm - 0.25mm (0.008inch - 0.010inch)

Exhaust: 0.28mm - 0.32mm (0.011inch - 0.013inch)

Feeler gauges; curved feelers gauges are better (I used; intake-0.22mm, exhaust-0.30mm), torque wrench, 10mm Jam nut tool (recommended but a 10mm ring spanner & flat screwdriver will do. The jam nut tool makes the process easier), 19mm socket, wrench & extension, and 16mm spark plug socket.

NB: The firing order for this engine is 1-3-4-2 and as such, the valve clearance check/adjustment will follow this order. Cylinder 1 is the one closest to the power steering pump.

Valve clearance check and adjustment should only be done on this model with the engine temperature at 38°C or less. Best done first thing in the morning!