help: tips, thoughts, advice on Random Misfire p0300, p0301, p0302, p0304 - Honda Accord Forum : V6 Performance Accord Forums
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Old October 20th, 2019, 12:33 AM   #1
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help: tips, thoughts, advice on Random Misfire p0300, p0301, p0302, p0304

i have been battling to fix this misfire and would appreciate any help, tips, thoughts on what could be causing. it started right after my TLS/RL Camshafts install

it usually happens during cold start up

what has been replaced from this List:

Common Problems That Trigger the P0300
Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
replaced 6x Spark Plugs NGK and 6x Ignition coils (used). do we have a distributor cap?

Incorrect ignition timing
i could not recreate the problem when i took it back to my Camshaft installer so hopefully it isn't this

Vacuum leak(s)
any thoughts from where if any??

Low or weak fuel pressure
any thoughts/suggestions?

Improperly functioning EGR system
swapped for a brand new Genuine Honda EGR for $300.00 - still misfiring

Defective Mass Air Flow Sensor
swapped out today at Acura since i have upgraded 3.7 TB and Manifold from MDX 2010. $50.00 brand new genuine Honda/Acrua part

Defective Crankshaft and/or Camshaft Sensor
i went to a junkyard and found the location of both our Sensors for V6 to be on the left side? if so, its behind the timing belt possibly?

Defective Throttle Position Sensor
i replaced this recently

Mechanical engine problems (i.e.ólow compression, leaking head gasket(s), or valve problems
it doesn't feel like any of these. Accord still runs great, just HATE seeing Check Engine Light blinking and/or coming on

Common Misdiagnoses
Fuel Injectors - picked up a used set plus rails but install is pretty extensive and would rather do Transmission Cooler install before this
Oxygen Sensor(s) - i believe there are four, 2 upstream and 2 downstream. one may need replacing due to sitting on my PCD and becoming melted a bit. maybe this is the cause of CEL?
also, i had an Exhaust leak from the Flex Pipe on my Tsudo J Pipe so that Flex Pipe was properly fixed for $200 since welding is beyond me

Powertrain/Drivetrain problems

Thanks for any help, suggestions, advice

at this point, i am at a dead end...
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Old October 29th, 2019, 03:05 PM   #2
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I know nobody uses this forum much anymore, so hopefully you figured it out. I am limited on my knowledge but it seems you threw a lot of money at it, so hopefully it has straightened out.

I can't talk to the new camshafts, but I had an issue with misfire and 02 sensor at the same time. If you have a decent OBDII reader, try to look for pressure in each cylinder and see if one is misfiring. Also, when re-setting your codes, make sure you're only in the Second ignition position and the car is not on, it will click.

I can't imagine I helped, but maybe help think of other ways to tackle.
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Old November 1st, 2019, 12:20 AM   #3
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Hey there. I actually just joined this forum, but I’ve had my accord for awhile now.

I recently had the same problem, except it was codes p0300 all the way to p0306. Turned out to be a faulty coil in cyl #3, but took awhile to diagnose, as the coil I replaced it with initially was cracked from napa. Was about ready to check timing when I noticed this. Ended up returning and exchanging it, code has gone away since it was cleared. I also replaced plugs as I have 260 thousand km and haven’t done it in awhile.

My advice would be to let the car idle, and pull off each connection to each of the coils individually. If you remove a connection and there is no change in idle speed, the cylinder is dead (no spark, air, fuel, compression). It is difficult to diagnose with the code reader I find, as one dead cylinder (In my case) causes the engine to change the timing and throw a code on each cylinder. However, you say the car seems to run ok other than the CEL, so this may not be possible.

If you are unable to diagnose the problem to the an individual cylinder/cylinders, I would begin to look into other possible issues such as vacuum leaks/air delivery, corroded/disconnected wiring to sensors, fuel delivery, compression, and timing. Perhaps something was missed after the cam install? Not trying to discredit your installer.

Oh, and try to do it in an order where you don’t have to constantly disconnect/reconnect stuff to check that certain components are functioning as intended. Saves a lot of time. Start with the easiest stuff and try not to get frustrated. Wait till she’s firin’ on all cylinders and then pay it back by layin a beating on er hahaha. The old Italian tune-up😂

Also I edited because I had a thought about the camshafts. Seems weird for this to happen around the same time. I would ensure timing is correct and double check wiring to camshaft sensors and such. Also thinking that the stock j30 ecu may not like the cam upgrade, although I cannot personally comment on this as I only have intake & exhaust mods. As far as I can tell from reading, no ones posted about issues of running upgraded oem acura cams on the stock ecu. Perhaps someone else may be able to speak more about this. I feel like the stock ecu would be able to compensate for the more aggressive profile, as long as the timing and such is set properly. Curious, are you on stock valve springs and such? Anyways, I feel like as long as the necessary steps were taken and everything was reinstalled as was, this shouldn’t be the issue. Seems like weird timing for the issue to occur without somehow being related though.

Best of luck. This is actually my first ever reply, hope it’s at least somewhat useful!

Last edited by 03cm866; November 1st, 2019 at 12:38 AM.. Reason: Edit- thoughts on camshaft install
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