Do a compression test could be a burnt valve

 

Also check valve adjustment

 

You’ve already replaced the spark plug and swapped the ignition coil on cylinder 2 of your 2004 Honda CR-V, but the misfire persists on cylinder 2. This rules out the two most common causes—bad spark plug and faulty coil pack. Here’s how to proceed with diagnosis and likely causes:
Next Steps in Diagnosis
1. Fuel Injector Issues

• A common cause of a persistent single-cylinder misfire after eliminating ignition components is a faulty or clogged fuel injector. The injector may not be delivering fuel properly to cylinder 2234.
• You can test this by swapping the fuel injector from cylinder 2 with one from another cylinder. If the misfire moves to the new cylinder, the injector is faulty4.
• Alternatively, listen for injector operation with a mechanic’s stethoscope or long screwdriver placed against the injector body; a lack of clicking sound indicates a problem3.

2. Injector Circuit or Wiring

• Inspect the wiring harness and connector for the injector on cylinder 2. Broken wires, poor connections, or corrosion can prevent the injector from working properly2.

3. Engine Mechanical Issues

• If the injector is working, consider mechanical problems such as:
  • Low compression due to worn piston rings, a sticking or burnt valve, or head gasket failure23.
  • Perform a compression test or leak-down test on cylinder 2 to check for these issues.

4. Other Less Common Causes

• Vacuum leaks near cylinder 2 (such as a leaking intake manifold gasket).
• Intake air leaks or issues with the air/fuel mixture specific to that cylinder3.

Summary Table of Next Diagnostic Steps

Step	What to Check	How to Test/Inspect
Fuel Injector	Clogged or faulty injector	Swap with another cylinder; listen for clicking34
Injector Wiring	Broken wires, poor connections	Visual inspection, continuity test
Compression	Mechanical engine problems	Compression or leak-down test
Vacuum Leaks	Intake gasket leaks	Visual, smoke, or spray test

Additional Notes

• If the misfire does not move after swapping injectors, and compression is good, check for less common issues such as ECM/PCM faults or rare wiring harness failures2.
• If you’re not comfortable with fuel system or compression testing, a qualified mechanic can perform these diagnostics quickly and safely.

In summary: After changing the plug and coil, the next most likely culprit is a faulty or clogged fuel injector on cylinder 2, followed by wiring problems or engine mechanical issues. Proceed by swapping injectors and checking compression to pinpoint the cause234.
Citations:

2. https://www.carparts.com/blog/p0302-code-cylinder-2-misfire-detected/
6. P0302 P0303 and P0304 MISFIRE?: Got This Code Recently. Changed ...

 

How do you make such good posts? AI??

 

I had a stubborn misfire issue on a 2010 very recently (thread here) that persisted after replacing spark plugs and swapping coils that ended up resolving itself about 15 miles or so after I poured a bottle of Techron fuel system cleaner into the gas tank. Might be worth a shot.

 

I had a misfire a couple of years back, replaced the plugs and coils, still had it.

Ran seafoam and other fuel cleaners thru the tank on a regular basis.

Also did Seafoam top engine cleaner - the one with the bent red tube, where you open the intake before the throttle body and spray it in there with the car running for 10 minutes then take a spirited drive and white smoke comes out.

Cured the misfire over time doing all that.