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Discussion Starter · #1 ·
Hello! I have noticed my engine hesitating sometimes and cold starts are usually rough. Feels like the engine is about the stall. Pressing on the gas helps bring back regular rhythm. Once warm, the car seems to run okay and I don't notice much problem when on highway. But when in gear (D) and stopping at a red light, the engine doesn't seem right and shudders once in a while.

Recently the car threw a check engine light, reporting a pending P0304 (cylinder #4 misfire). The car was shaking vigorously while driving and pressing the gas peddle helped a little. So I took out the ignition coil and saw that it was slightly rusted and there was some condensation and the coil boot was soaked with engine oil.

Took a look at all the other cylinders and it seemed like #2 and #4 were the only two that had quite a bit of engine oil in the spark plug wells. And the SAME two cylinders' ignition coils were previously replaced (1.5 years ago) and the car has been pretty much just sitting in the garage cause of COVID. All spark plugs were also replaced at that time. I haven't been able to take out the spark plugs to check - waiting on some socket extensions.

I cleaned out the two wells and swapped the coils from from #4 to #5 but haven't gotten a check engine light yet. The random shudder/rough idle is still there. I also checked to see if the ignition coils were working properly by disconnecting them while the engine was running - all seemed okay.
So..
  1. Can the misfires be caused by the oil in the sparkplug wells? (e.g. poor connection) And would replacing the valve cover + tube seals fix the issue?
  2. Can engine oil in the spark plug wells kill ignition coils?
  3. Could this be some other problem such as an exhaust leak? Or fuel system issue?
  4. Any other thoughts?
  5. Aside - is there a way to tell if the engine needs a valve adjustment?
The car has 188K KM on the odometer for reference.
Thanks for your help!!
 

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Hello!
So..
  1. Can the misfires be caused by the oil in the spark plug wells? (e.g. poor connection) And would replacing the valve cover + tube seals fix the issue? YES
  2. Can engine oil in the spark plug wells kill ignition coils? YES
  3. Could this be some other problem such as an exhaust leak? Or fuel system issue? NO
  4. Any other thoughts? NO
  5. Aside - is there a way to tell if the engine needs a valve adjustment? FEELER GAUGE TO MEASURE THE GAP.
The car has 188K KM on the odometer for reference.
Thanks for your help!!
 

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Pull the plugs and look for oil on the side electrode. 188km isn't necessarily high mileage. But you may have bad oil rings. If the plugs have been in there for some time, try changing them first.
 

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Discussion Starter · #4 ·
Thanks for taking the time to go through the post and for responding to the questions! Much appreciated :)

Pull the plugs and look for oil on the side electrode. 188km isn't necessarily high mileage. But you may have bad oil rings. If the plugs have been in there for some time, try changing them first.
Will do that later today once my socket extensions come in and will update the thread. The plugs have only been there for one and half years and saw maybe around 2,000 KM of driving.
 

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Discussion Starter · #5 ·
Pull the plugs and look for oil on the side electrode. 188km isn't necessarily high mileage. But you may have bad oil rings. If the plugs have been in there for some time, try changing them first.
So I took a look at the spark plugs. One of them had more carbon deposits than expected but overall not very much. The oil on the side from cylinder 2 is likely from the well itself and not the combustion chamber.

I've attached photos of the spark plugs from cylinder #2 and 4. Also included #5 as a negative control.

Cylinder 2.jpg Cylinder 4.jpg Cylinder 5.jpg
 

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Pilot without a plane
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Where did you get the coils from?

I had a bad experience with parts store coils. Ended up scavenging some OEM coils from a junkyard. Problem solved. I wrote about it in my car's thread.
 

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Discussion Starter · #7 ·
Where did you get the coils from?

I had a bad experience with parts store coils. Ended up scavenging some OEM coils from a junkyard. Problem solved. I wrote about it in my car's thread.
Good point. They are Autolite platinum plugs that my mechanic put in last time the car was serviced for its broken ignition coils.

Aren't the OEM plugs iridium? Can the downgrade cause these issues?
 

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Pilot without a plane
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NGK laser iridium plugs

The car may not be happy with those plugs, but I was asking about the coils. When I installed new Carquest Premium coils, it ran fine for a day or two. Then I started getting misfires on every cylinder like the plugs were bad so I installed new plugs. No change. I reinstalled my OEM coils and it ran fine.
 

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Discussion Starter · #9 ·
NGK laser iridium plugs

The car may not be happy with those plugs, but I was asking about the coils. When I installed new Carquest Premium coils, it ran fine for a day or two. Then I started getting misfires on every cylinder like the plugs were bad so I installed new plugs. No change. I reinstalled my OEM coils and it ran fine.
Oh my bad. Read that incorrectly. They are some Spectra brand coils. They haven't given me much problem. I also tried switching around with the OEM Hitachi one but noticed no difference.
 
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