Help! Oil on spark plug threads...

Every pent roof design engine made will at some point leak oil into the spark plug wells some get so bad they cover the plugs with oil older 426 hemi's were famous for it and so was the 3TC Toyota engine it won't misfire because oil is a dielectric. It's normal and no big deal except for a little smoke after you change the plugs.

 

this ^

I changed mine at 60K and this is how they looked.

Denso


NGK:

 

There spark plug tube seals where the tube meets the valve cover. The tube themselves are sealed by silicon where they meet the cylinder head. It could be leaking there, it's very common.

 

Sorry buddy, but you are wrong. Fuel Oil(conventional or crude oil) has a conductivity value of 0, it's even used to insulate coils in transformers. It is not a dielectric. http://www.smartmeasurement.com/en/wizards/flowmeter/flmtr_mag_conductivity.asp

Oil commonly causes vehicles to misfire.

 

Tube seals if u ever have oil in the spark plug tube it's the tube seals trust me I see it all the time mechanic

 

That was oil on those threads right? My truck has never misfired in it's life

The check engine light flashes i think when it misfires and I have yet to see that

 

Normal ops. All a byproduct of combustion. Pull a plug on a lawn mover it does it also. Unless there is any oily deposits on the plug porcelain just drive it like you stole it.

 

ya, those look normal.

 

Threads is not the same as the electrode.

The cel flashes when a condition exists that can damage the catalytic converter, be it a misfire, or lean/high temp condition.

Large amounts of oil in the combustion chamber will cause a miss i.e. Leaking valve stem seals, blown head gasket, etc. Just because you don't have a miss doesn't mean there isn't oil there however they are not mutually exclusive.

 

The PCV valve is located above that particular spark plug hole. When I recently replaced my PCV is noticed an oil drip mark on the valve cover leading directly into the hole. The oil leaks from the PCV threads into there.

 

You are correct wrong word but right issue. I'm left handed you know.

 

necrothread


update, just did my third sparkplug change on my 2013 v6 and yup, the two plugs closest to firewall had slight oil on the threads,
nothing excessive (except any oil is technically excessive) all plugs looked nice and clean (used and tan) as they should on the hot side