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Update: So I went full steam ahead today. Got the new valve cover gasket ($20.99 at AutoZone), unscrewed all the 10mm bolts, pried the cover off, hey! No obvious breaks in the seal! Well, that's good I guess?

So per my advice here, I go to replace the spark plug tube seals. Might as well since they came with it. There's no obvious breaks, but it feels pretty stiff. Took a screwdriver to it. So brittle it started to break into little pieces immediately. Must need replacing then! Couldn't get it to come out, did some more YouTubing, then oh...

Turns out my seals are non-replaceable. Aaand I just tried to remove one. Woops! Three auto-parts stores later, a valve cover is in stock. $60. Put the new seal on it, cleaned the spark plug tubes that had oil (not too much since cleaning them out a week ago), and it's still stumbling.

Since switching the coil pack from 1 to 2 last time, my errors now show 1 and 2 are misfiring. But no more 3? Last time it was 1 and 3, and now one is okay? Since that didn't make sense, following the AutoZone guy's advice for now: topped it off with fuel (in case of bad gas at last fill up) then waiting until after I've driven it at least 60 miles.

Any new ideas? I guess it could still be the coil packs, but I have trouble believing they'd just decide when to fail and when not to. And the car did run better today, just not completely better. And the check engine light still blinks on startup, throwing 3000, 3001 and 3002. :/

Original Post

I read a few other forums and answers here.

My 2008 Accent just hit 180,000 miles. It's been leaking oil (very slightly) for a while, but has never caused any major issues, so I haven't gotten it worked on - frankly I'm afraid of "needing" a repair that's worth more than the car.

It has had fits with misfires from time to time on the highway, but after it cools off it usually does fine again.

The other day it did it right when I cranked it. I had just filled it with gas prior. It isn't shaking horribly, but the OBD reports cylinders 1 and 3 misfiring. Did my research, tested coil packs. All give about the same resistance (~2.5 Ohms), assuming no issues there. Cleared the codes, switched the coil packs on cylinders 1 and 2. Code shows up on 1 and 3 still. Not the coil packs.

Replaced the spark plugs. Looked like they had never been replaced (bought the car used at 120k, you'd think they'd have needed to before then?). Yay! Should be issue solved.

There was some oil on the coil packs and the plug on cylinder 4 was covered in oil. Maybe I found the leak! Research shows it could be the valve cover gasket. Didn't have time to replace it while I was doing the plugs, but it's been okay until now, I figured I'd fix this then try to replace the gasket this weekend.

New spark plugs in and it's still a-rumblin'. Tried some gas treatment in case it was the gas, but that hasn't worked either.

Could it just be a bad tank of gas? Or could one of the coil packs still be bad? Or could the leaky gasket cause the misfires?

If it matters, temps got below freezing the night before the issue occurred. Really trying to figure it out, I don't want to hurt it any more before I get it fixed.

Thanks!

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    The wells should have separate seals in them which would need replaced. These should come with a valve cover gasket kit. Don't neglect them or you'll have fixed nothjng.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Jan 10, 2017 at 23:41
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    Do you have a multimeter? If you clean out the plug wells and the misfire doesn't go away do a voltage drop test on the coil ground wire for cylinders 1 and 3. They share a common splice in the harness. Can you confirm that cylinders 1 & 3 are actually firing?
    – Ben
    Commented Jan 11, 2017 at 0:11
  • Do you mean the voltage drop between coil ground (on the coil pack) and battery ground? Or some other voltage?
    – Ives
    Commented Jan 11, 2017 at 8:47
  • @Ives yah b- to coil ground terminal koeo or running
    – Ben
    Commented Jan 12, 2017 at 17:30
  • I tested the resistance on the coil packs (mine only have two leads, there's one per cylinder), and they all read around the same, ~2.5-3 Ohms. I have to unhook them to get at the contacts, how would I test them against the battery ground?
    – jlehenbauer
    Commented Jan 14, 2017 at 23:34

2 Answers 2

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The oil in the spark plug wells can absolutely cause misfires. Replace that valve cover gasket; my guess is it'll be problem solved. If not, no problem, it's certainly not wasted effort. Post back with your results!

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  • Will do! If you had to estimate, do you have an idea of how long this replacement would take an amateur able-bodied youtube-taught mechanic?
    – jlehenbauer
    Commented Jan 11, 2017 at 0:06
  • It looks pretty straightforward, so probably an afternoon, but plan for a full day to be safe. Also, have another car nearby because you will most certainly head to the store at some point for things you didn't expect. Oh yeah, and disconnect your battery before starting. When I did my wife's Camry I accidentally shorted the alternator and spent another few hours replacing its wacky fuse. Take your time and be methodical about it, and it should be no problem. I highly recommend getting a Fel-Pro gasket if you can; I've had very good luck with them.
    – atraudes
    Commented Jan 12, 2017 at 1:40
  • Yeah, going to attempt this Saturday, and luckily I have an extra car to use for AutoZone runs! I didn't when I replaced the belts on my car last time, so had to reassemble everything halfway through when I realized it wasn't one big serpentine and needed to drive the car to get the second belt :P
    – jlehenbauer
    Commented Jan 12, 2017 at 13:40
  • Did some work today, updating the post to reflect it!
    – jlehenbauer
    Commented Jan 14, 2017 at 23:23
  • Just saw your update, congrats on getting it done! I've heard about those gaskets being built into the cover; it's pretty frustrating and odd that they included the gaskets in your kit. No matter, $60 for a new cover isn't too bad at all. I've heard of folks forking out over $200 per bank. Since it's still happening I'm somewhat inclined to agree that it's fuel related. Hopefully some driving will clear things up. If not, the injectors may be next. Either get them cleaned or start by swapping 1 and 4. Injecting too much or too little fuel can cause a misfire.
    – atraudes
    Commented Jan 16, 2017 at 22:02
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A good spark plug is always a good idea. On this particular car the NGK iridium plugs are the best recommendation i can make. They should be gapped @ .042. A common component that seems to go bad on this car is the crankshaft position sensor and it can cause misfires, and hesitation. It literally takes all of 10 minutes to change out

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