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Discussion Starter · #1 ·
I have a 2002 Honda Accord EX V6 auto sedan with ~267k miles giving codes P0401 (EGR Insufficient Flow) and P1399 (multiple random misfire) 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 with Honda OEM ~ 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 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.Coils are ~$90 from Honda online.

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

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. 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 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.
Hello,

Though it's possible you have two separate issues, my guess is that there's a problem with the EGR system that's also causing a misfire. Do you have a scan tool that's capable of displaying the EGR valve position sensor voltage?
 

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Discussion Starter · #3 ·
Yes. I'll test that this weekend and post back. EGR valve is only 35k miles old but yep that's certainly possible.
 
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Discussion Starter · #4 ·
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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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.
Thank you for updating us.

I chased EGR codes on my V6 Accord for many months. Cleaning the passages underneath the intake plenum and the EGR valve itself was insufficient in my case. I eventually gave up because I wasn't noticing drivability issues, but when I was forced to repair a coolant leak from the water passage near the EGR, I found a complete blockage behind it. Cleaned it up and it's never come back.
 
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