On Halloween, the check engine light on my 2007 Honda Odyssey EX started flashing. Read the codes which were a random misfire and misfires on 2,4,5, and 6 (P0300, P0302, P0304, P0305, and P0306 respectively). Symptoms were rough idle, no loss to power. The car is at 117k miles, we had just bought it a month earlier, so I replaced the spark plugs since I did not know when the were last replaced. In so doing, I found that the coil pack well (I think that is what it is called) for cylinder 5 (front-center) contained oil. The rubber boot on the bottom of the coil pack had swelled as a result and was stuck in the well on the plug. I eventually got it out, changed the plugs, put it all back together, but it was still misfiring. Took it to a shop that replaced the coil pack in cylinder 4 (front-left) and informed me that the valve cover seal needed to be replaced, not now, but within a few months (I am never going there again). Things were fine for a week, then the codes were thrown again (not sure what the new codes are, assuming them to be the same until I can get them read tomorrow).

Really rough idle until warm then not so bad, flashing check engine light while under load or stopped, then steady or off while coasting. Changed the valve cover seal on Saturday. Still rough idle, not as rough, but still rough (gets better the more it is ran), with the light doing the same as mentioned before. The rubber boot for cylinder 5 is again stuck in the well (couldn't get it out this time) with the rubber boot for cylinder 6 (front-right) missing altogether (it was there when it was taken to the shop, again, not going back).

I'm pretty sure it is a coil pack that needs to be replaced but I am not sure how to check which one. I'm thinking that it might be the one in cylinder 5 just because that is the one with the oil in it (couldn't get it all out because the boot was stuck), but I'm also thinking that it could be the one in 6 because it doesn't have the boot and so it is not making a good connection to the plug.

2 Answers 2


The issue was that another coil pack had gone out, probably because of the oil in the well.

After getting all the oil out of the well, the engine was still misfiring. I then proceeded to unplug the coil packs one by one while the car was running. The only pack that didn't have an effect on the engine when it was unplugged was for cylinder 2 (back-center). I swapped that with the plug for cylinder 4 (front-left) and unplugging the coil pack from cylinder 2 on cylinder 4 still had no effect while unplugging the coil pack from cylinder 4 on cylinder 2 did effect the engine. Replaced the coil pack that had no effect, and the engine runs like new!

  • I am glad you solved the issue, just a question, why did you say you were never going to the mechanic that suggested changing the valve gasket/seal, also usually coil packs come in pairs? if you are changing one might as well change all of them too
    – method
    Nov 20, 2016 at 1:57
  • It was mainly just because of the time frame that they gave me for changing the valve cover seal. Within a week the well was almost full of oil and when I pulled the cover off, half of the seal was missing. Granted, I should have looked my self, but I am no mechanic and wouldn't have known what to look for in the first place.
    – JRLambert
    Nov 21, 2016 at 5:34

if you just bought it return it immediately and don't bother. Only reason to keep it is if you got a heck of a good deal. Else go back and complain and get some money back for the issues or have them fix it.

If it was a really awesome deal as in literally $1500 or less then ok you have an oil leak and that is shorting things out. You may get lucky and be able to pull one thing and replace a gasket.

I would personally not touch this for more than $1k and you can pull them into small claims court and drag them over coals to pay for the repairs in most cases.


The fix

You should mop up the oil as this is causing shorts. This might be a problem with a leaking valve cover gasket or someone who spilled oil. Does the oil look clean and clear like new (some oil is a dark blue) or brown / black, cruddy, used? If it looks new mop it up should be fine if used most likely its a valve cover gasket.

I do not think the coil pack is the problem and never needed replacing to begin with. instead the oil was creating a faster way for the spar to get to the head (ground) and had less resistance than the plug gap. The car still runs ok because some of the spark is still going over the plug but it is very weak.


Keep all your receipts and call the person you bought it for and talk maybe they will cut the price down to a reasonable $1500. The car on KBB if all interior and exterior is in great, not quite perfect, shape is worth only about $4k

  • I would, but unfortunately the vehicle was bought from a private seller, not a dealer. We are stuck with it.
    – JRLambert
    Nov 7, 2016 at 6:05
  • no your not. Most states have a lemon law and you can haul them into court for selling a defective car as if it was good. This is called deception. If you're in California then all sorts of things you can do including telling them it needs smog still which will require them to fix it since it is against the law here to sell a car without passing smog even if the add says as is or you sign paperwork saying you will take care of it those are instantly invalid due to the CA smog laws.
    – Cc Dd
    Nov 7, 2016 at 6:07
  • @CcDd - The lemon law wouldn't apply here. California is it's own breed, no doubt. In most States, there is no buyer's remorse: if you don't get a "we owe" slip from the dealership (you'll never get one from an individual), you'll never get it fixed through them. You've bought it "as is" unless it comes with a warranty. Most of the so called warranties provided "free" from the dealerships are not worth the paper they are written on. Nov 7, 2016 at 14:17
  • @Pᴀᴜʟsᴛᴇʀ2 you can still drag them through a small claims court stating you were duped into thinking this car was in good condition when it wasn't. if the ad originally said everything works or no mechanical issues or something like that you can argue that that is above the as is. If courts let people get away with these types of bait and switch techniques there would be lots of issues. Bait and switch laws are on a federal level I believe. Same with selling a product that is not fit for purpose. In this case I would argue "I bought this as stated, you lied and sold me that".
    – Cc Dd
    Nov 7, 2016 at 21:09
  • 1
    Sorry for the late response on this, but I found the problem. I cleaned out the oil from that well but the car was still misfiring. I then proceeded to unplug the coil packs one by one while the car was running and found that when one on the back bank was unplugged it had no effect on the running of the engine. Swapped it with one the caused the engine to drop when unplugged, and it had the same effect in its new location. Replaced it with a new one and problem solved!
    – JRLambert
    Nov 19, 2016 at 1:03

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