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So I can’t figure this one out. I have a misfire on cylinder 4 and cylinder 4 only (throws the P0304 code)
It’s intermittent, which is adding to the fun – here’s what I have tried.
Moved coil pack from cylinder 4 to cylinder 5 – misfire stays on cylinder 4
Moved the plug from cylinder 4 to cylinder 5 – misfire stays on cylinder 4
Made sure the pair (plug and coil from cylinder 4) moved to cylinder 5 – misfire stays on cylinder 4
Moved the injector from cylinder 4 to cylinder 6 – misfire stays on cylinder 4
Verified the signal from the car to the coil pack is correct on cylinder 4 (pin 1 shows battery voltage, pin 2 is connected to ground)when I checked the injectors, there were a lot of deposits on the nozzle plate – cleaned all 6 injectors, replaced the o-rings, and reinstalled (did that when I was swapping injectors)
I moved the injectors today – over the past few days, I ran a tad under half a tank of gas with a bottle of techron (the one for up to 20 gallons)
Drove around this afternoon, all over town, and the van behaved flawlessly. Then this evening, it’s back. still cylinder 4.When I pulled the intake plenum, I noticed that the runner going to cylinder 4 was pristine (no deposits) while all the other 5 cylinders had deposits. Going further into the intake, and the trend follows. I did the valves about 9k miles ago, and they had all looked the same (cylinder 4 looked like all the others) – I also checked the valves on cylinder 4, thinking maybe I messed that one up, but it measured right where I put it 9k miles ago.
What could it be? I haven’t done any other work on the van, nor has anyone else. I can’t think of what it could be that would be intermittent like this.
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Just a thought…
Considering you’ve swapped the electronics and the miss still occurs on the same cylinder.
Just for giggles might do a compression test and leak down test on the cylinder in question to see the mechanical condition.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.
I don’t have a leak down gauge, so I can’t do that, but the cylinders did seem to hold pressure after each time I checked compression.
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)
At least the basics appear good.All of the plugs appear identical – no deposits/ash/oil.
Another good sign.And of course, the van is running beautifully this morning… idle is smooth, no misfires, etc. I just don’t get it.
But isn’t that the case when your attempting to trouble shoot anythingI 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.
Might suggest trying garden variety tap water through the intake, it cheaper and does a wonderful job when done correctly.
I don’t have a leak down gauge, so I can’t do that, but the cylinders did seem to hold pressure after each time I checked compression.
[color=orange]A compression gauge has a schrader valve ( unless you’ve removed it. )
So what ever the highest reading you got will remain on the gauge until you release the pressure.
You can modify it to work as a leak down gauge by removing the schrader valve and installing a T fitting on the hose with another schrader valve to allow compressed air into the cylinder [/color]There’s definitely a schrader valve, and I have not removed it. The spec from honda is 120psi min, no more than 29psi difference between cylinders – I am reading closer to 200psi (forgot to hold the throttle open, so maybe a little more than that) with under 10psi between high and low.
I’m intrigued by the water method – I think there’s a video that Eric did here, but I haven’t found/watched it yet
Here ya go …
Suggest you use the vacuum line from the brake booster and a spray bottle to spray the water into the hose.
You need to do voltage drop test on the ground side. You said you did the valves. Make sure your valve timing is correct. Then make sure your did the ignition timing was done correctly. Make sure both these are correctly done. If all checks out you need to do a standing and running compression test and compare it manufacture specs. If this checks out then you have missed something doing with the ignition system.
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Not entirely sure what you are recommending I do – when adjusting the valves, I adjusted clearances – you don’t touch timing. I changed the timing belt, etc. about 40k miles ago, so I am pretty sure timing is fine.
For now, the van appears to be running fine. I didn’t get a chance to try the water as a top end cleaner yet – I have run two half-tanks with a large container of techron in each, and am now running a half tank with BG12 in it. I did pull the three large connectors going to the PCM and cleaned them thoroughly using electrical contact cleaner, as well as the three plugs on the PCM. Maybe there was debris in one of the connectors giving me an intermittent contact, maybe the injectors were fouled (lots of crud in the nozzle plates I had to clean off), or maybe one of the intake valves was sticking due to carbon fouling on the valve stem (I was thinking the latter, since the #4 intake runner was so clean when compared to the others – my thought being a sticking intake valve might allow some of the fuel to be pushed back into the intake runner before it closes, which would tend to clean it up). I think the electrical parts (injectors, coil packs, and plugs) are all fine given that shuffling them around didn’t make a difference, and the mechanical seems sound (to the limits that I can test it) based upon the valve clearances being correct, and the compression test being solid, and very uniform cylinder to cylinder.
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