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Discussion Starter · #1 · (Edited)
UPDATE 6/16/21
Compression, Spark, Fuel - that’s the key to all engines. Compression is 210# each cylinder. Spark - this this is funky because I checked the plugs the first time I started working on this problem and they were clean then. Last weekend I pulled them and the back 3 were carbon fouled. I cleaned and regapped all plugs after checking the compression. Then I pulled each injector and cleaned each one. Put it all together and I had indiscriminate misfires. Now I’m mad. Today I replaced the MAP just to verify. Took it for a test drive. Had a hard second shift. Never made it into third because it bogged down and misfired - big time. Compression is high I assume because of the valve job. New plugs and new coils. No the plugs were NKG not Bosch. Fuel is coming through. MAP was replaced. Valves were clattering during the drive and it never shifted to 3rd gear. Eight codes - all misfires, two general and one for each cylinder. I am down to a jumped timing belt - other ideas are welcome. Moral? Be careful who you allow to work on your car.

UPDATE: This pilot had a valve job done last year with new plugs. March 2021 the 1399 code appeared - misfire any cylinder - which leads me to rule out the plugs. The compression was checked in March and is 200 in each cylinder (you would think the valve job was good with this compression). I was on vacation during April so the vehicle set. The coils were replaced May 1st. The EGR and PCV were replaced May 4th. It still runs rough rough today May 11th. I sprayed starter fluid around the vacuum lines on May 4th to no avail. The air tube was broken in one of the creases before all this happened, I assume, however I repaired the crack with silicon. I have compression, spark, and fuel but a rough running engine that will not increase above 3000RPM. Catalytic converter readings are similar in both sides so I ruled out cats. Does anyone have another troubleshooting clue? May 11th I ran a vacuum and it was a steady 12in even with misfires.


I have considered replacing the engine but having to drop the engine is new to me. Pulling the engine is a process very familiar to me. I would appreciate hearing about the process from someone who has dropped the engine and lifted the body.
 

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This pilot had a valve job done last year with new plugs. March 2021 the 1399 code appeared - misfire any cylinder. The EGR and PCV were replaced. The coils were replaced. It still runs rough. I have sprayed starter fluid around the vacum lines to no avail. The air tube was broken in one of the creases that I repaired with silicon. The compression is 200 in each cylinder. I have compression, spark, and fuel but a rough running engine that will not increase above 3000RPM. Catalytic converter readings are similar in both sides so I ruled out cats. Does anyone have another troubleshooting clue? I have considered replacing the engine but having to drop the engine is new to me. Pulling the engine is a process very familiar to me. I would appreciate hearing from a process from someone who has dropped the engine and lifted the body.
y only concern would be the air intake tube repair. Are you sure it’s completely solid? If any air is bypassing it, it could cause your misfires, and your rough running issue.
 

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Discussion Starter · #6 ·
y only concern would be the air intake tube repair. Are you sure it’s completely solid? If any air is bypassing it, it could cause your misfires, and your rough running issue.
That has been my thought also, but I sprayed the air intake tube with starter fluid and no change - so I assume no leaks.
 

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Discussion Starter · #7 ·
Sometimes owners have experienced issues with non-OEM spark plugs and/or coils. The air intake tube is relatively inexpensive to replace.
On a 1399 code? I could see one or two misfiring for nonOEM coils or plugs but to have it throw a misfire on various cylinders? That is why I thought vacum or exhaust. What do you think?
 

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Replace the air intake duct (aftermarket is cheap), and the give the MAP sensor a good cleaning, since it sucked in unfiltered air for who knows how long.
 

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On a 1399 code? I could see one or two misfiring for nonOEM coils or plugs but to have it throw a misfire on various cylinders? That is why I thought vacum or exhaust. What do you think?
That was my thought too, the chance of all the plugs simultaneously causing misfires on all cylinders, pretty slim. You said the only code you have is 1399, so it’s not a consistent enough misfire on each cylinder to throw a code for a specific cylinder. It’s gotta be something with the intake in my opinion. Can you get a hold of a scan tool and look at the live data of each cylinder to see if the fuel mixtures are running lean, or rich? That would narrow down if you’ve got too much air, or fuel. And if you think plugs are the issue, they are easy to replace and relatively cheap. You could always just buy one, and throw it in and see if the misfire goes away on that specific cylinder before you bought all 6 lol
 

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Moreover, claim your Piloteers 5% discount if you order from Rockauto. It says it expires May 12th, but check the same post if needed later, as they typically replace it when it expires. Careful of fake NGKs on Amazon.

 

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If the valve job was done correctly, I'd say it's the Bosch plugs as well.
 
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I never knew Honda’s were so picky about their plugs. Crazy!
My Hyundai came with Bosch plugs as OE. I replaced with NGK Laser Iridiums and it runs better too now, lol. I have a low opinion of Bosch electrical parts. An OE Bosch O2 sensor failed, and I replaced with Denso.
¯\(ツ)
 
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Did you replace the EGR valve before or after this problem started?

If you can drive it, does the problem get worse if the engine is under more of a load, like going up hill, compared to a flat road?
 

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Discussion Starter · #17 ·
Did you replace the EGR valve before or after this problem started?

If you can drive it, does the problem get worse if the engine is under more of a load, like going up hill, compared to a flat road?
After. Load increases the misfiring.
 

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P1399. Hmm. Well let's assume the valves are still correctly adjusted And timing hasn't jumped a tooth.
Have you checked each plug for spark
Are you getting a P030x code as well?
Things I'm wondering is whether an injector(s) have gone bad. If you have a P030x pcode moving the injectors around could move the misfire and reveal bad injectors.
 
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