Honda Odyssey Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
13 Posts
Discussion Starter · #1 · (Edited)
Hi all - Wondering is the collective wisdom here can help me solve an intermittent misfire issue on a 2011 EX, ~105k, without installing too many unneeded parts.

The short version is my scan tool is currently seeing intermittent misfires (~1.5 misfires per mile of mixed city/highway - bank 2 is usually has about 2x the number of misfires as bank 1.) Without the scan tool, I'd think the car is driving totally fine - it feels smooth both on the road and at idle - and no codes.

Longer version is I did the timing belt, adjusted the bank 2 valves (have not touched the bank 1 valves), and installed new plugs a few hundred miles ago. When I pulled the bank 2 valve cover off, I noticed damage as discussed here: Valve cover needed? junkyard, or RockAuto to cyls 5 and 6. Right after that job, I took test drove the car for ~40 miles and it felt fine until I came off the highway and refilled gas. I had essentially no power after the gas stop (totally undrivable – couldn't even limp it), and had the car towed back.

The van threw codes for various p030x, bank 2 cat inefficient, and EGR stuck open. It turns out that the bank 2 downcat had overheated, melted, and clogged the downstream cat. The EGR valve was also stuck open, probably with a chunk of cat debris.

Since then, I've replaced the melted downcat, cleared out/cleaned the downstream cat, and rechecked/readjusted the bank 2 valves, and cleaned the EGR valve. Car drives fine, but the misfires are worrying. However, I don't know if the car was misfiring before this all started.

I've also:
Rechecked timing – marks all line up.
Did a CKP erase/learn
Did an idle learn
Run a leakdown test – it's good.
Swapped coils from bank 1 to bank 2 – no change
Tested with old plugs – no change
New B2 AF sensor (one one galled)
Readjusted B2 valved to loose end of spec
Run an EGR valve test – failed (but no code?? – maybe it's not reacting fast enough)

I'm suspecting that this is either a secondary ignition issue related to the deformed valve cover but am somewhat confused by the cyl 4 and bank 1 misfires (I'm aware that the ECU doesn't always identify the correct bank, but I'm thinking that the numbers are too high and too unrelated to the firing order for just misidentification).

I'm also wondering if a slow EGR valve could cause this. I don't know why the scan tool is failing it, but the van is not running rough. The only exception is for the 1 second when the EGR test function ends and I return to idle. I'm guessing the EGR valve is closing too slow leaving it more open than it should be when the test ends and the van returns to idle.

Also, is this level of misfiring a significant issue? My worst cylinders are probably getting a misfire or two every few miles. If not, I not sure it's worthwhile to replace the valve cover/coils.

What are your thoughts/suspected culprits and ways to confirm without buying a new valve cover, coils, EGR valve, etc? Thanks!
 

·
Registered
Joined
·
2,068 Posts
all those misfires, might explain why you had to change the catalytic.
no mention of muzzling the VCM, start there.
O2 sensors, then look at a bad PCM as your next cause.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #3 ·
all those misfires, might explain why you had to change the catalytic.
no mention of muzzling the VCM, start there.
O2 sensors, then look at a bad PCM as your next cause.
I'm guessing that it was misfiring quite a bit more on that test drive. I'd think that a cat should be able to handle an extra injector pulse or two of gas once in awhile - just not . I'm seeing pretty similar cat temps between b1 and b2 right now. 1000-1100 idle, 1500-1600 onramp. I'm guessing those numbers are being read from the AF or O2 sensors.

I forgot to add that I readjusted the valves from the tight end to the loose end of spec after the cat replacement - and had a better tool set for the readjustment. That didn't change the misfire rate. Also, replaced B2S1 AF w/ the downcat - old one galled.

Readings from AF and O2 look as expected.
 

·
Registered
Joined
·
2,068 Posts
From what I understand of VCM, that would cause misfires on cyls 1-4, right? I'm seeing my highest misfires on 5 and 6, so....
that's right 1-4.
didn't see any exact codes, so threw out some guesses.

where did these plugs come from? iridium or ruthenium?
did you move the plugs around?

original motor?
check your body grounds, esp the one for the pcm.
injectors like you mentioned, easy to swap around and see if the problem moves around with the swap.

if you dont have the service manual, this may help out...
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #6 · (Edited)
that's right 1-4.
didn't see any exact codes, so threw out some guesses.

where did these plugs come from? iridium or ruthenium?
did you move the plugs around?

original motor?
check your body grounds, esp the one for the pcm.
injectors like you mentioned, easy to swap around and see if the problem moves around with the swap.

if you dont have the service manual, this may help out...
Thanks.

There are no codes now, so it's harder to track down. The codes it threw earlier were linked to EGR valve jammed open, and blocked back cat. LT and ST fuel trims look reasonable. Any suggestions on what to PIDs to capture/chart out along with misfire counts?

New plugs are NGK laser iridium, same part number as OE. I did bank swap the plugs on one of the coil swap tests.

Original motor, original owner, regularly maintained at/above the maintenance minder level. Doesn't consume oil.

Grounds look good (visual inspection). Not sure it's worth pulling/reseating them. It's not a rusty car.

I have not swapped injectors yet. Thought about it, but saw some stuff about needing seal kits and risk of breaking injectors.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #9 ·
Just getting back at trying to figure this out again after taking a few months to do other things.

Disabled VCM, checked the grounds, replaced the EGR valve, tested w/ old plugs, and probably a few more things...

I'm still seeing the same rate of 1-2 misfires per minute/mile (maybe ~60-100 per hour of mixed driving [total across all cylinders]). My earlier statement of cylinders 5 and 6 being higher is probably wrong. It just depends on the drive, but they look random. I don't see a corelation of misfires to engine load or RPM, except that it doens't misfire at all at idle.

I'm thinking this is a higher level issue than one cylinder or bank, but the intermittent nature of the misfires is making it hard to track down.

Anyone have ideas on what data to monitor/record or tests to try?
 

·
Registered
Joined
·
2,068 Posts
Just getting back at trying to figure this out again after taking a few months to do other things.

Disabled VCM, checked the grounds, replaced the EGR valve, tested w/ old plugs, and probably a few more things...

I'm still seeing the same rate of 1-2 misfires per minute/mile (maybe ~60-100 per hour of mixed driving [total across all cylinders]). My earlier statement of cylinders 5 and 6 being higher is probably wrong. It just depends on the drive, but they look random. I don't see a corelation of misfires to engine load or RPM, except that it doens't misfire at all at idle.

I'm thinking this is a higher level issue than one cylinder or bank, but the intermittent nature of the misfires is making it hard to track down.

Anyone have ideas on what data to monitor/record or tests to try?
PCM
 

·
Registered
Joined
·
2,068 Posts
I was a bit hasty with the PCM conclusion, however random misfires all over the map usually indicate a bigger underlying problem.

you should report back all codes for review.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #13 · (Edited)
I was a bit hasty with the PCM conclusion, however random misfires all over the map usually indicate a bigger underlying problem.

you should report back all codes for review.
Sadly (or not), there are no codes. I'm seeing the misfire events in the PGM-FI datastream. I'm watching the total misfires for each of the cylinders since startup and/or the agregated total misfires for the engine since startup. If I didn't have a scantool that could see this, I would not have known of the misfires since the van drives fine. (I'm not fully confident that the van is actually misfiring. Maybe the PCM just thinks it is misfiring?)

I only bought this tool after the downcat issue, so I don't know whether this issue predates the timing belt work/melted downcat. I now suspect that the EGR broke first and caused the cat failure, but that's since been fixed.

UPDATE: I just did the first long (~90 min) test drive after installing VCM Tuner II. Almost all my bank 2 issues have gone away (very few misfires, and only or at least mainly at close to WOT), and bank 1 might be better than before. Misfire counts are:
C1 36,​
C2 25,​
C3 15,​
C4 4,​
C5 2,​
C6 1.​
There are far less misfires on the highway than city.

Bank 1 has orig widebank, cat, and O2 and cat, and has not had the valves adjusted. IIRC, the bank 1 downstream signal isn't as clean as the bank 2 (with new sensors and cat) isn't as good debating whether to do valves first, or sensors.
 

·
Registered
2016 Touring Elite
Joined
·
1,599 Posts
It might be time for a bit of math... That was total misfire counts, right?

assuming 2000 RPM avg for the drive = 180000 revolutions for the 90 minute drive = 90000 ignition events per cylinder.

Worst cylinder misfires = 36/90000 = 0.04% misfire rate, or 1 misfire every 2500 ignition events.

It isn't throwing a code, so why worry about it?

-Charlie
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #15 ·
It might be time for a bit of math... That was total misfire counts, right?

assuming 2000 RPM avg for the drive = 180000 revolutions for the 90 minute drive = 90000 ignition events per cylinder.

Worst cylinder misfires = 36/90000 = 0.04% misfire rate, or 1 misfire every 2500 ignition events.

It isn't throwing a code, so why worry about it?

-Charlie

I was doing the same math in my head as I was driving. Yes, those are total misfires and yes, it's probably a rate that is low enough for the cat to handle....

I guess I'm a little concerned because it's still quite a bit higher than it should be, I don't have a definitive reason why the bank 2 cat melted, and I regularly am far from home with that car.

Does anyone know what the damage threshold is for a cat?

Thanks!
 

·
Registered
Joined
·
2,068 Posts
a bit perplexed by this thread...

you're asking for guidance on an issue that's a non issue?

do you count the rotations of your wheels as they spin while driving at 80mph, anticipating that they may fly off under the right conditions?

If you want to debate the data regarding misfires, just do so and not make it like your troubleshooting an issue.

Bizarre!
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #17 ·
a bit perplexed by this thread...

you're asking for guidance on an issue that's a non issue?

do you count the rotations of your wheels as they spin while driving at 80mph, anticipating that they may fly off under the right conditions?

If you want to debate the data regarding misfires, just do so and not make it like your troubleshooting an issue.

Bizarre!
Thanks. Good to know this isn't an issue. There isn't a lot of information in the forums on how many misfires are acceptable, and none of my other cars have anything close to this number (especially before VCM disable).
 

·
Registered
2011 Odyssey LX, 120k miles
Joined
·
1,962 Posts
I'm pretty sure the following is true for these engines, and it may help you think about what is going on and whether you want to do anything:

Misfire detection is done by monitoring the crank position sensor. The idea is that if everything is running and firing properly, with all cylinders equally powerful, then the crank will spin at a constant rate, at least per cylinder (each 1/3rd rotation will take the same amount of time). But if a misfire were to happen, a particular cylinder would get less impulse / force / torque and the crank speed would vary slightly. Slowing following the misfiring cylinder, then speeding up on the next one. Some logic in the ECU analyzes the CPS signal, for example detecting two misfires in a row, and decides to set a code and light a light, etc.

So, separate from your situation, this detection and isolation system is not perfect. It is very common for a problem with a certain cylinder to trigger misfire codes on multiple cylinders. There is variability in any engine as it spins, some more than others. Maybe your engine runs a little rougher than it should, so maybe it really does need some improvements - valve adjustment, coil replacement, spark plug replacement, or piston / valve issues. But I think if the ECU (PCM) actually thought you had a problem it would turn on the CEL and set codes. So your measurements may be completely normal for a perfect engine, or maybe they indicate somewhere between perfection and code-worthy.

Based on the info you posted so far, I'd make a note of it and wait until a code is actually thrown, and not worry before then.
 

·
Registered
Joined
·
2,068 Posts
^^^ This 👆

apologies for my sarcasm, oldskewel is much more eloquent in his summary of your concerns.

it's quite possible something is out of spec, however in the absence of cel codes, you are going to be chasing a phantom.
 

·
Registered
Joined
·
13 Posts
Discussion Starter · #20 ·
Thanks 2011.2017.odyssey and oldskewel.

This gave me confidence to road trip the van, and it drove fine for 500 miles, but started setting a P0420. This is for the cat that wasn't changed, so it's not terrible suprising.

What's puzzling me at the moment is the AF and O2 waveforms. I've read that the O2 should be fairly flat (not mirroring the AF output). On bank 2 (new Dorman cat), and O2 basically mirrors the AF. However, bank 1 (orig cat) has spikes in the O2 output. The two AF sensors are pretty close.

162470


If the O2 should be fairly flat, doesn't that mean that my new bank 2 cat is in worse shape than the bank 1 cat? (I've read that the aftermarket cats aren't great, but if so, why am I not getting a P0430? )

Am I misreading this data?
 
1 - 20 of 20 Posts
Top