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A bunch of P030x codes

3K views 19 replies 9 participants last post by  John Clark 
#1 ·
My wife's 2005 EX-L has an intermittent CEL and I finally got around to pulling the codes.
Logged codes show P0300, P0302, P0304, and P0305 but it also has pending codes of P0301 and P0306.

I'm not even sure where to start. I did replace her plugs with NGK's I think, I'm going to have to pull them to make sure but assuming the plugs are good, where do I start to look on this one?

 
#2 ·
The EX-L for that year has the VCM that turns off cylinders to conserve fuel and that system is known to foul plugs and burn oil, so definitely check your plugs. I'm pretty sure those are all mis-fire codes. You haven't noticed any missing or rough idling/running of the motor? The other common issue for mis-fires is the coil packs.
 
#3 ·
Given that your model has VCM, I recommend you buy and install a VCM Muzzler device. Otherwise your misfires will continue or get worse. Plus VCM causes piston ring failure, excessive oil consumption and damaged engine mounts. You need to nip this in the bud. All those misfires codes are telling you something.
 
#4 ·
There has been some shuddering so there's definitely an issue.
I'll double check the plugs and if they look OK then I'll maybe see about replacing the coil packs but it would seem odd for 3-4 of them to go out around the same time. I'll also look into the VCM Muzzler.
 
#6 ·
If you are getting the codes and shuttering, one or more of your coils is bad. You can use the coil drop test to find the bad coil and then replace it (quite easy). There are a few threads here on bad coils, read through them. This is a relatively common occurrence on the vans after some miles and time. Replacing the coil does the trick. Sounds like you have the plug thing addressed.
 
#8 ·
Not making any assumptions. I'm going to pull one of the plugs tonight now the engine is cold and verify the type. After that I'll go through the coils and check those. Ive had to replace one recently on my 2007 Maxima so am familiar with the problem of coils.
 
#9 ·
How many miles on this vehicle? Everyone thinks just because there is a misfire that there must be a bad coil. Usually the coils are not the problem. A symptom of a bad coil would be a cylinder specific misfire (it happens on the same cylinder all the time) and will either be all the time or when warmed up.

In this case, you have multiple cylinders misfiring. Often the cause is VCM related in cylinders 1-4 but since you also have 5 & 6 misfiring it makes me think that may not be it. If you're over 150K miles and it has never had a valve adjustment I would lean toward adjusting the valves. Random misfires on all cylinders is a common symptom of a 170-200K mile vehicle that's not had the valves adjusted.
 
#10 ·
Thank you for mentioning valve adjustment. I'm looking through all the paperwork she got back from the dealer after my wife got her oil change it is mentions operation ADJVLV6 - Adjust valves EXL/Touring 05/06. This is one I may not want to attempt myself since I usually don't do the engine stuff but they're wanting $650 just in labor to do it.

I did pull the spark plugs and it looks like I got the wrong ones. Entering the VIN into one of the Honda parts sites it tells me I should use NGK LZFR5K11 plugs but I've got LZFR6K11. I'm not sure that they'll really make that much difference. I'm thinking this valve adjustment is the way to go.

Now, on the plug I pulled out, I noticed a small black mark but I don't think there's anything that shows anything unusual for this plug? I didn't have time to pull the others. This was from the front right (as you're looking towards the vehicle), sorry not sure which cylinder that is.

View attachment 148199
 
#11 ·
How many miles on the van?

Yes, the 5K11 are the proper plugs for that. These cars are sensitive to the plugs used. I'd change them out.

If you're under 150K I don't think the valve adjustment is the issue. If you're over that then it's the first thing I'd do. It needs to be done anyway.
 
#15 ·
The new spark plugs are on order. Is there really a big difference between LZFR5K11 that should be in and the LZFR6K11 that are in there. (I'm in north Texas if that helps any!). The muzzler is on the way also. I went with one of those smart ones that connects to the battery. Weather here is variable, it can fluctuate 50F in a day or two when a front comes through.

Once the new plugs and muzzler are in I'll clear the codes and go from there.
 
#16 ·
The difference in the plugs is the heat range. I'm not saying that's definitely the problem but using the wrong heat range plug can definitely cause issues. The 6 is a colder plug. You didn't buy the plugs on Amazon or eBay, did you?
 
#18 · (Edited)
These codes virtually came on together, at about the same time, right?. If I got one, then another a month later, that would seem somewhat normal. But all six on at once, within a week - or several months??? This seems quite unusual to me. I like the wrong plug theory.

It is not going to be a valve lash issue. Replacing the coils is not likely to solve this problem, either. I thi9nk it's likely that the wrong plugs are the cause (and maybe because they are gapped differently than the correct ones)? Maybe these codes are being set in traffic, where engine and coolant temps will rise? The old plugs weren't particularly fouled, (with no thrown codes), but a colder plug could foul more rapidly. Then, all six codes shouldn't be set (or be ready to be set) almost at once as you describe, because plugs won't foul at the same rate. The two pending codes indicate that whatever is causing this, is not too far off from being "normal", and it's continuing. That fits with the "wrong plug" theory. And the plugs were the last thing you did before getting these codes, further indicating a plug issue...

When you solve the problem, please let us know what did it!
 
#19 ·
Since I had to pull the coils to replace the plugs I checked the three front ones and got the same readings on all 3 coils so I'm sure they're not the problem.

I changed out all 6 plugs, only took an hour or so. I checked the gaps on the new and they were all within spec. The LZFR5K11 plugs are now in and I cleared the fault codes. My wife said she hasn't noticed any issues with it idling, missing, or juddering like before. What a difference just 1 number makes. She hasn't really taken it for any long drives you but fingers crossed that, with everyone's help, I've solved the problem. Thank you.

 
#20 ·
That's great news...I'm not surprised, though. These engines are extremely sensitive to what plugs are run. I use only the exact plugs specified. Don't buy on Amazon or eBay as most are fake.

Good work!
 
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