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Engine light on, scanned and found p0300, p0301 0302 0304 0305 0306. And p1399. Engine missfire, all cylinders except #3 cylinder, checked coils with ohm meter allsame readings, installed new plugs.
Cleared codes all good for a couple of days then same codes back, removed top intake cover and cleaned all passages, suspect carbon build up.
Some mornings runs rough for a few seconds, then clears up, did drop test all cylinders are firing, could it be bad injectors?
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PCM reflash? honda has a TSB on the issue (i think it costs around $100 to reflash) also if you check ohms(resistance) on injectors they need to be over 10ohms anything less will cause driveabilty issues.
UPDATE
checked valve clearances all very close to spec’s,all within .002″ engine very clean inside, check all injectors found all had the same reading, all read open, 1 on all ranges
cleared codes
started engine, was running rough, but as it warmed up it got much better, but I got engine misfire codes.
cleared codes.
ran engine for five minutes and it ran fine, did drop test on coils all cylinder working, no codes.
but I will get codes again on cold start, any ideas?First, checking resistance on coil packs is useless as it will not often reveal a bad coil. Coils fail under load and a resistance check will not reveal that.
Honda’s rarely have fuel delivery issues so I would table the injector theory for now. Also, it would be very rare for the issue to be caused by valve clearance. If you get the clearance wrong, you can damage the engine. In fact, you can actually cause a misfire with misadjusted valves.
I’d start your search by looking for vacuum leaks. Any vacuum leaks can cause an issue like that. Also, it was brought up that this might be something that could be cured with a reflash. For that you might consider calling the Honda dealer with your VIN to see if your vehicle is one that is effected by that issue.
Lastly I can’t stress enough how using quality parts on a Honda is important. If you have anything other than NGK or Nippon Denso plugs in the engine you might start by replacing those with the correct parts.
More info on solving issues like this here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Keep us posted on your progress.
Update #2
Today I started it and it was running rough, missing on at least 1 cylinder maybe more, after a minute or two as it warmed up it smoothed out and was running smooth
I did a drop test again and all cylinders were firing, I know I should have done it while the engine was missing,
I did a compression test 220-225 psi so there is not a compression problem, I spoke to the local Honda dealer, he said could be a 02 sensor, ? I don’t have an 02 code, only misfiring codes
thank for your help, regards Stevechanged one coil, seems to be breaking down at start up, after 1 minute of running it starts to work
It sounds like a classic vacuum leak to me. Try spraying water around the intake manifold gasket when the engine is cold to see if the water hits something that changes the way the engine sounds and runs.
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