find my thread on engine misfire. I ended up finding that it was a fuel injector. When I bought a replacement at Advance Auto, it was oem honda injector in Honda packaging inside the box.

 

here you go
http://www.odyclub.com/forums/52-2005-2010-odyssey/289730-engine-misfire-case-study-p0306.html

 

That was a great post - thanks! Maybe what I'll do this weekend is pull the plenum and swap injectors between 4 and 5 and see if the misfire moves, and if so, swap out the injector. As you pointed out, it would be interesting to know how a misfire is detected by the engine - I can disconnect coil packs, the engine idle goes down, but it doesn't throw a code (pending or otherwise) reliably - maybe the detection algorithm only looks periodically, and it has to be disconnected when it's looking... who knows. The diagnostic tree starts having you check wiring harnesses after this, and looking things over, I don't see any damage. I did replace a coil pack plug a little while back, but that was on cylinder 5, and you don't really stress the cable when relocating pins from one connector to another...

How were you measuring the misfire - I have a different code reader (AutoXray EZ Scan 4000) - I have had to wait until the van acts up enough that it stores a pending trouble code.

 

In order to see any misfire counters you need a factory capable scan tool. Most global OBDII readers will not give you enough info.

As for misfire detection, the computer monitors the cam and crank signals and looks for instant slow-downs as the crank sensor goes past each cylinder's firing sequence. They are not always accurate but have gotten better over the years. \

My guess is you might be able to see the injector problem using a current measurement with a scope but Honda puts many different items on the same circuit as the injectors so you have to sort through all kinds of other "noise" on the scope waveform. Without a graphing meter or scope you're stuck with pulling injectors and swapping them to see if the problem moves to another cylinder. Have you checked compression? Even if you don't have a compression gauge or scope you can check compression just with your ear during a crank sequence. Pull your coil fuse or injector fuse or fuel pump fuse and then just crank the engine and listen to it. It should sound even on every cylinder's compression. If you hear reh-reh-reh-reh-reeh-reh-reh then you have a compression issue. If they all sound even then it's possible to still have a compression issue but most likely not.

 

I haven't checked the compression yet. I am going to go ahead and move the injector - I will check compression after that (I plan to do that in the morning, then I'll drive it a bit to warm it up, and check the compression). I have two sets of o-rings for when I move injectors (drove the van to/from the store for that and it worked just fine... no issues at all. I haven't been able to get the van to do it when I drive, just when my wife is driving it (it's her daily))

My scan tool is an older model (I can't even find AutoXray any more - I think they got bought by Actron, but there's no info on legacy product) - I have looked into Torque Pro, but it's not clear what it can/can not see (I have played with torque lite, but it's pretty limited). I was looking at the manual for my scanner, and while it does show various misfire things, that's in the extended software package which they only had for domestic makes, and now I couldn't even get that since they appear to be gone!)

 

For full features on Honda the Foxwell NT510 is probably the best scan tool for the money (under $200.) It does global OBDII on any vehicle and will do full bidirectional factory data on the vehicle make you purchase it for. You can add other makes for $60 each, up to 5, I think. A few here have purchased it based on my recommendation and I don't think anyone has been disappointed. Amazon has them...just make sure you buy one with no make installed or Honda preinstalled.

 

Here's a thread going on right now where there is a compression issue and it's easy to spot with a trained ear during the crank:


http://www.odyclub.com/forums/9-pro...s/9-problems-concerns/310105-starting-issues-after-timing-belt-replacement.html

 

I will just use my compression gauge. everything sounds normal.

Sent from my SM-G900V using Tapatalk

 

Ok - pulled the intake plenum - interestingly, the intake runner to cylinder 4 was pristine, while the the others had the normal carbony sort of deposit on them.

Pulled the fuel rail and injectors for the front bank - there were a lot of deposits (brownish) on the ends of the injectors - particularly on the nozzle plate (not sure what it's called - the metal disk with the 8 tiny holes in it) - swapped injectors 4 and 6, then cleaned all three of them using intake cleaner and q-tips and a plastic spudger. Figured I should pull the other fuel rail and inspect that, and sure enough, they were all gunked up, too. Cleaned them the same way, replaced the o-rings, and reinstalled the rails. Showed the wife the deposits on the injectors when I pulled the second rail and explained that she needs to start paying attention to where she gets gas (and I am probably going to more religiously run injector cleaner through the van)

I was concerned that since I had adjusted the valves about 9k miles ago, that maybe I messed up cylinder 4, so I pulled the valve cover and remeasured - they were right where I left them. Buttoned everything back up, fired it up, and its running well - idle seems very smooth. Let it idle for a while with no incident.

So for now, my wife is out driving around so we'll see if it throws a code. I am wondering if maybe the injector is sticking and releasing fuel after it should, and the extra fuel is washing the intake runner... hopefully the fuel system cleaner will do its thing and free it up if that's the case.

One thing that sort of pissed me off - for pretty much all of the injector sockets, the locking tabs were embrittled and snapped right off. I safety wired (used an insulated solid core copper wire) to hold them each in place, since there is a lip on the end of the injector where I can have the wire go and not be right up against the leads... if I have to replace an injector, I might go ahead and replace all of the connectors (if I can find them).

for now we wait and see if it throws a code again. I didn't get a chance to check compression yet - maybe tomorrow (definitely tomorrow if it throws a code while the wife is out and about)

 

My van also had the same crud on the end of the injectors but they weren't really gummed up, wiped off easily with a rag. The holes in the injector didn't look blocked. One of the intake ports were cleaner than the others. The intake manifold port was clean as well as the intake runner port IIRC.

 

Interesting! It was a really stark difference in the plenum, and the difference looked pretty similar to yours for the lower part of the manifold, with the leg for cylinder 4 being quite a bit cleaner. It was really weird on the plenum - it was pristine with no deposits in cylinder 4! We drove it a bunch this afternoon, and it was a pretty hot day. I just drove it to fill it up with gas (ran through a bit under a half a tank with a big bottle of techron in it, so that is hopefully cleaning things up) - filled it up with 12 gallons and another big bottle of techron (the one that treats up to 20 gallons) - will run this one through and see how it goes.

On the injectors, the guck on the plastic parts wiped off for the most part (just a thin layer) with a rag no problem, but the stuff at the end was more persistent. There were a number of injectors where one or more of the holes in the pattern of 8 seemed completely obstructed - afterwards, checking with a magnifying loupe, all of the holes looked clear - hopefully it's not too gummed up inside the injectors.

The van is running noticeably smoother now - didn't give the rough idle or throw any codes. Crossing my fingers that this was it!

 

Hopefully that was your only problem! Run a few tanks of fuel injector cleaner and don't forget to drive the van hard. B12 chemtool and BG 44K seemed to work the best in my experience. My original plan was to deep clean the injectors by removing them but after seeing the tiny holes clean, I didn't bother with it.

 

And it's back. Not sure what to try next. I went ahead and checked the harness to the coilpack on cylinder 4, and it seems fine - pin 1 shows battery voltage, pin 2 shows ground. No changes when I wiggle around the harness or the connector. Tried cleaning the contacts, but that didn't help either. The rotten thing ran flawlessly all day today - no sign of issue. Then this evening, the misfire is back. I am wondering if maybe one of the valves is sticking now and then or something like that... maybe one is really carboned up? my hope is that the fuel system cleaner will take care of that. After watching the vids above, I am thinking the chemtool stuff is the next thing to try. I am not sure if soaking in a container of the straight material is the way to evaluate them, but there is clearly a difference, and it's hard to imagine one of the others doing better after being diluted in gas...

ugh.

 

Did a compression test this morning (warmed the van up, pulled the fuel pump fuse, removed all the plugs, then went around, doing 5 cycles per cylinder - checked all 6 multiple times) - compression was nominally identical cylinder to cylinder (about a 4% difference between the highest and lowest)

All of the plugs appear identical - no deposits/ash/oil.

And of course, the van is running beautifully this morning... idle is smooth, no misfires, etc. I just don't get it.

I am leaning towards maybe the cylinders are carboned up, and for whatever reason, cylinder 4 is particularly bad... considering running a top end cleaner and seeing if that helps.

 

Use a borescope camera to look inside the combustion chamber. Remove the spark plugs and stick the camera down there. Check it now and then after the fuel injector cleaner has finished.

 

Do you think it's deposits on the cylinder itself that would be causing the issue? I was thinking maybe on the valves, but would I be able to see that with a consumer borescope (can they look upwards fairly well? I have seen one at harborfreight, but I am guessing it's sort of junk...)

 

If the build up is severe, then I think it would cause the issue. I think the carbon build up dilutes the air/fuel mixture and causes the misfire to occur. (correct me if I'm wrong)

I have something similar to this: https://www.amazon.com/Inspection-D...GZD7VHBGTHPHC8AM&pd_rd_w=SdtZG&pd_rd_wg=tD1N6&psc=1&refRID=W5HEGZD7VHBGTHPHC8AM Inspect the top of the piston for excessive carbon build up. You can see the edge of the valves on the cylinders that have the intake valves open. To get a good look at the valves, you need to take off the intake manifold and stick the borescope camera down the intake runners. Looking at the bottom of the intake valves will be difficult, some borescope cameras might have attachments to look upwards.

 

You can get cheap boroscope cameras on ebay that are USB and plug into a computer. Seems to me if you bend the cord and tie it facing the other way and put it on a coat hanger that you could get it to look up.

I sort of don't think the issue is mechanical though.

Have you checked fuel pressure?

Can you perform a leak down test? A burnt valve might read good on compression but cause an occasional misfire.

 

Unfortunately, I don't have a leak down gauge set. I have not checked fuel pressure yet - will do so this week if I have a chance. Wouldn't be too surprised to see it low (van has a bunch of miles on it, and while I have changed the filter, I have not changed the pump or pressure regulator) - I was thinking if it were a low fuel pressure issue, I'd be seeing a random misfire, with more than just one cylinder impacted. Not much else to check, though. I checked and cleaned the three connectors to the PCM, but didn't see anything amiss with them (just cleaned them for good measure).

I was wondering if the PCM could be the problem, but wouldn't think that would be an intermittent issue.

 

Just to confirm, you swapped injectors 4 and 6? Are you continuing to receive misfire on cylinder 4?
Are you getting multiple cylinder misfire code? You really gotta look at the car running with diagnostic tool
to inspect real time misfire counters. You maybe chasing your tail with particular cylinder misfire.
Another thing is the clean #4 intake runner.
I vaguely recall that fuel is a cleansing agent, so too much fuel will cleanup carbon build up. I maybe completely
off base here though.

 

... You really gotta look at the car running with diagnostic tool
to inspect real time misfire counters. You maybe chasing your tail with particular cylinder misfire...

This is so true. Just because it's throwing a P0304 doesn't always guarantee the misfire is on cylinder #4. It could be the cylinder before or after it in the firing order. The firing order is 1-4-2-5-3-6 so I'd look at cylinders 1 and 2, as well, though the clean intake runner on #4 is still a clue that doesn't support this theory.

This vehicle may need someone who is good with a scope on ignition and injector pulses to see if they can track down the issue.

 

Without misfire counts for all of the cylinders its difficult to rule out fuel pressure so I would check that next.

The ECU grounds the injector so it could be an issue. I would rule out everything else before swapping one in.

 

The clean intake runner for cylinder #4 has been bothering me for the last couple of days too, but I can't put my finger on why it would be clean. The deposits are due to the PCV system putting the crankcase air back into the intake manifold. Fuel does wash carbon buildup but the deposits are prior to the injector, aren't they? When I pulled my upper intake manifold to do the valve adjustment I found all 6 lower intake ports dirty. I just left them.

As a side note, I just watched a fresh diagnostic video on a Honda CRV that had a bad ground on one coil pack. This one was pretty hard failed but you could have something similar either on the injector or the coil pack.

 

So, the misfire is very evident when it occurs? Can you duplicate it while working on it? If so, simply unplug a coil pack to verify the cylinder. Then, it would be nice to know if that coil pack is firing during the misfire event and if the injector is firing during the event. Since you've moved everything around and the misfire stays that means it could be a wiring issue to either the injector or the coil. This thing needs a scope or graphing meter attached to monitor it when the misfire starts.

 

when it's doing it, it's very evident, but I can't make it misfire. It was misfiring on Thursday (mid morning when the wife called in a panic) then was fine Thursday when I got home from work. On Friday, it was mostly fine all day, but did have a code when I checked it in the afternoon. On Saturday, it was fine in the morning, I moved the injectors, and it was fine all day driving around, until late in the day then it did it a bit. Sunday it was smooth as glass - did the compression test, etc. and drove it a bit during the day without incident. Only thing I did to it last night was pull the three big plugs from the PCM and clean them thoroughly with electrical contact cleaner, as well as the plugs on the PCM itself, let them dry, then plugged them back in. My wife drove all around today without a problem, either.

The clean intake runner suggests fuel is getting up there, which makes me think a sticking valve, so hopefully the cleaners are taking care of it. I want to try something more aggressive on the top end - I have seen a bunch of things on using water, as well as some of the top end cleaners... not sure what I'll try.

 

I think you should have a pro scan tool hooked up to the van to see whats going on. You can try the cleaners but keep the catalytic converters in mind, you might clog them up. I don't think they will clog up if you follow the directions on the can.

IMHO, just use the fuel injector cleaners that you put in the tank. You can put the whole can of fuel injector cleaner to a half tank of gas so its more concentrated.

 

Well - everything is running fine since the weekends festivities. Maybe there was something in one of the three plugs to the PCM - an intermittent contact or something like that - or it was a carboned up/sticking valve that's freed itself now with the injector cleaner... so far, two half tanks, each with a large container of techron have gone through the engine, and I just put in 10 gallons (on top of a little my wife put in yesterday) with a can of BG12... if it stays ok, maybe I'll run another tank with fuel system cleaner through it and call it good. The van is running perfectly now - idle is smooth and constant - seems to be ok...