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2000 Honda Accord misfire code

2000 Honda Accord V6 Code P1399 and misfire codes. Code is not supported by Honda ( no info)

Yes, info, Took me 10 seconds to Google it,

When is the code detected?
The control module monitors the crankshaft speed and has detected a misfire condition
Possible symptoms Engine Light ON (or Service Engine Soon Warning Light)
Lack/loss of power
Hard start
Engine hesitation

P1399 HONDA Description
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring. - Valve clearance out of range

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On a Honda this old, valve clearance is highly likely.

Thanks Mustangman but we have done valve adjust three times in the last year, the code disappears but comes back again with misfires. This time it goes away but comes back within 5 miles. We have changed spark plugs recently and also the EGR valve. More ideas please. My mech seems to think possible ECU . Huba

Have you performed a dry compression test

If it’s low . . . and I wouldn’t be surprised it it was . . . it may be due to burnt valves

Valve lash can be correct, and you can still have a burnt valve

If compression is below specs, squirt a little oil into the cylinders and perform a wet compression test. If the numbers raise dramatically, the problem is bottom end. If nothing changes, the problem is top end

You can then perform a cylinder leakdown test to determine where the problem lies

I very seriously doubt that is the cause . . . a lot of modules get needlessly replaced, because the mechanic has performed an improper and/or incomplete diagnosis


Agree with @db4690… You didn’t say how many miles the engine has on it so maybe it is a wear issue. Burnt valves, leaky valve seats, leaky rings ect.

The code is to identify a condition - this condition.

The cause is assumed to be valve clearance. If your mechanic set the valve clearance once and the problem came back, that is a big red hint that valve clearance is NOT the issue.

Your mechanic charged you for at least one valve clearance job and maybe 2 you did not need. Sounds like he also didn’t do a basic compression test as @db4690 db is suggesting. He is guessing. My idea is that it is time to find a better mechanic.

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No, we have never done a compression on this engine, so as per suggestion, we will do one. Now let me give you alittle more background, we have always had a code P1399 when these misses appear.So, we have tried to deal with that code which according to Alldata is not supported by Honda . I haven’t looked but I think this engine has around 165,000 miles which shouldn’t have burned valves on cylinders 2,3,4 and5. I don’t think 1 and 6 show up as misfires. So, off to check the compressions and I’ll get back to you. Really appreciatethe help. Huba

Glad you appreciate the help.

We would appreciate the entire story up front instead of dribs and drabs over 3 posts of what you’ve experienced and done to this car to solve the problem. Chasing our tails doesn’t help you nor does it make us eager to help.

BTW, As I posted, the valves might not be burned, but they might not be sealing very well either. Same for the rings.


Agreed with db4690 and Mustangman. It’s always best to weed out any potential mechanical issues before spending money (maybe a lot…) that accomplishes nothing.

If the compression is down it also could be due to cylinder bore issues. Rings, etc. At 19 years of age and 165k miles it’s certainly possible. Hopefully not.

If the compression is low enough it can cause misfires due to incomplete combustion.