'02 Accord V6 P0401/P1399 Driveability Issues

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Jan 3, 2004
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northern Alabama
I have a 2002 Honda Accord EX V6 auto sedan with ~267k miles giving codes P0401 and P1399 with driveability issues. I've performed the EGR port cleaning throughout the car's life a few times even TSB 99-085 where the pipe kit is used in the manifold. EGR valve was replaced ~ 35k miles ago when I also cleaned the intake manifold last. But the P1399 code is different this time (I'm pretty sure) and driveability issues appeared quickly. So, I cleaned the intake manifold and all this weekend. It wasn't terribly clogged (seen worse on this car). Test drive revealed no issues and no code. Drove it to work this morning and code is back within 3 miles but no driveability issues until ~ 20 miles in. Car is running rough, bad miss, low on power, etc. This doesn't change if at idle, in neutral/drive, A/C on/off, etc. Same issues on the way home but driveability issues developed withing a couple miles of leaving work. Hmm.

New Honda EGR valves are now ~ $210 ($177 5 years ago) from online Honda parts departments.

Any thoughts on what else might be the issue? I don't see this P1399 code in the factory service manual.

Thanks.
 
Joined
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P1399 on a Honda is a random cylinder misfire code :unsure:

Is there a vacuum leak or anything cracked? Any ignition or fuel-related problems?
 

benjamming

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I had wondered about the coil. I would've thought it would be limited to just one cylinder though presenting misfire for cylinder x.
Plugs were replaced at ~210-230k miles with Denso Iridium long life 3396; SKJ16CR-L11.
 

wlk

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Aug 21, 2016
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I had an old Isuzu Ascender-Trailblazer, w the 4.2l straight 6 it did the random misfire code for old plugs. I'd start there, as you state plugs could have 50k miles on them and the max I change at is 50k on Iridiums, 30k for everything else. In that 4.2l w Iridiums as oe, when I started changing at 50k my mpg stayed consistent, couldn't believe the difference almost 4mpg's. Per RA- Platinum is oe plug type, i would switch back to those and go w NGK as they are probably oe plug mfr, maybe Denso. The plugs&wires/coils were not designed for different plug types, even if percieved as better and it can cause issues w them. I learned yrs ago to stop believing the hype of better plugs than what was OE as it can create problems w the ignition systems. Some will say different but when you have a problem and spend money on diagnostic and parts and it comes down to the vehicle not performing on a stupid plug, you learn. Especially Honda's they are picky w lots of things.
Once you replace the plugs and if it comes back, I'd look at my coils. If they are old- personally I would just replace them while I was at the plugs. Hopefully it is something easy and not catastrophic. Let us know what you find
 

benjamming

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I've waited a few days to confirm the issue is gone. Ended up pulling the coil connectors one at a time and suspected cylinder #2 was the issue. Wiped off the coil (had some oil/fuel on it). Swapped it with coil #5. Problem didn't follow as all cylinders showed issue when coil connector was removed. All codes were cleared and issue and codes have not returned.
 
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