2008 Accord 2.4 L
150000 kms. CEL flashes. I pull over, and have car towed home. I put code reader on, it confirms P0301 misfire. no other codes.
I changed plugs that were original I think. swapped coils, cylinder 1 remains as misfire.
Did a spark test and confirmed spark. I did resistance test on injectors, all were good. Tried to swap injectors from cyl 1 and 2. no difference, code remains. cleared code with reader, and it comes back after a rough start. CEL still flashing.
Oil change done recently. NOTE: changed battery since I had car in garage for repairs. Also, Engine does have the 2 second VTC noise on cold starts.
I am stumped on this. I will do compression test tonight after work.

 

Turns out to be a burnt valve that caused the misfire. Dealer wants 1500 for labour, + 500 more for a machine shop to redo the head, plus 500 or so in parts. NICE!!!
I will be doing this work on my own (other than the head rebuild), so any tips would be appreciated. Only scary/foreign thing is the timing chain and what to do with it when removing and replacing the head.

 

Are you positive it's a burnt valve?
If the valves have not had their routine adjustment done, verify it's just simply not that.
If plugs and COPs are fine the next step to check after a misfire code or infamous P0420 is to check valve lash and even verify the MAF is clean.
A burnt valve will make a 'choof' sound from escaping compression. Since you only recently received the P0301 I would be surprised that the valve would be burnt so soon.

 

Thanks.
Dealer confirmed the burnt valve with a camera inside the chamber. I was unable to do the compression test myself, because the tester I had would not fit the spark plug threads of this head. I checked the valves myself, they were very close to spec. Exhaust valves were a bit tight, but nothing to cause it not to fire. What is the infamous P0420? I did not get that code on either one of my code readers?

I will have the head off soon, just struggling with the chain and camshafts. got a Chilton's manual on the way. There is no info or help online for this model doing head removal.

 

If they are tight when cold, then they will be even tighter or hang the valve open when hot.
That would cause a loss of compression which would cause a misfire, or worse a burnt valve. But usually you would have plenty of time between a misfire code and a burnt valve.

More common on the earlier Speed Density cars the PCM couldn't readily diagnose problems with the engine so even if an active misfire was occurring often the first code that the PCM would punt would be 'Catalyst below threshold efficiency'. Unscrupulous, or ignorant, shops would claim the catalyst was dead/failing and would need to be replaced. When in reality it was most likely the engine just needed a simple tuneup.
Catalyst can only work correctly if the engine is in tune and putting out an expected exhaust. Crap in(out of tune engine) Crap out(exhaust below threshold efficiency).

They are out there, just have to know where to look.

 

Exhaust valves burnt. 1 has the giant chunk missing. That is why it did not fire. Previous owner ran the original plugs and I never thought to check them.

Lots of fun getting it off. Will be more fun t get it back together properly.

 

That looks more broken than burnt.
Surprised the other chamber is so carbon fouled as well.
While you have it apart inspect the timing chain, VVTI sprocket, guides and tensioner.
K engines are nice, they have more of the components integrated, lot less random wiring looms and bracketry getting in the way like on the older cars. Timing chain components are a bit of a ***** compared to the older belted engines.

 

I assume you have never seen a burned valve. That is what you are looking at.

Technically,yes it is broken,however it becomes that way from super heating and burning. Hence the term. Occasionally the valve will only warp,but the majority of the time a piece breaks off. Additionally the misfire didn't cause the burned valve,the burned valve cause the misfire. My guess is the valves were out of adjustment.

I pulled this out a b16 about a week ago:

 

You can utilize OEM Honda factory information or an aftermarket data base that sells OEM Honda information. Either one is perfectly acceptable for this job. I would not rely on a Chilton.

Click on the links: (IMO Alldata is the better value)
https://honda-tech.com/forums/tech-m...-link-3330938/

 

Well she is back together and runs nice. Also replaced vtc sprocket and solenoid.
thanks for the help!

 

Wow, glade you figured it out. I am also having the same issue and this thread will help me trouble shoot the issue. I hope its just a valve adjustment and not a burnt valve.

 

that's how I got my car for 50$. Brother in law sold it to me when it chipped an exhaust valve. I tested compression before I took it all apart. all the other cylinders have 145-150. I literally just cleane the valve seat and replaced the valve, no machining. New gaskets and now the all 4 have 145-150 compression. Oh I also did a seafoam soak to the pistons while I was waiting for parts (about 3 days of soaking) car runs great.
1995 civic lx 5 speed 398k miles