So I started getting a cylinder one misfire a few days ago. It got bad enough to where the car was falling on its face and stuttering under load or any throttle past like 30%. So I bought a set of NGK Iridium plugs, and set to work changing them out.

All of the plug wells looked clean and dry, with the exception of cylinder 3 (passenger side of the engine, farthest back to the firewall). It was totally flooded with oil - about as far up as the hex section of the plug for tightening it in.

The old plugs, NGK R, also came out looking extremely old and worn, covered in white lean corrosion, and the gap read an enormous .070, .075!?

Does this happen over time, or were these plugs put in there at that gap? Its strange too because the car actually ran very good with the old plugs in. It runs solid with the new plugs, but maybe feels a tad less powerful.

Any help is appreciated!



Plugs were horrible

Ridiculously large gap

Flooded spark plug well

Flooded

 

The spark plug well filling with oil is caused by the valve cover tube seal failing. With these cars, that seal is built into the valve cover, requiring the valve cover itself being replaced.
I had the same issue with the engine cutting out above ~3k, and several of my plugs looked about the same as yours; HUGE clearance. The gaps open up over time/use, normal wear for plugs.
The car should be running better with fresh plugs in it... not sure why it would be down on power after.
FYI the farthest rear cylinder on passenger side is actually #5

 

I thought I replied but must not have sent the message before.

So I need to replace the actual valve cover, not the gasket?

Yeah its definitely running better. I may try bumping the gap up to .50 and see how it feels but it is pretty darn healthy feeling now.

The only thing I am noticing now is when I come to a stop and idle for a minute, I will get a large misfire where you can feel it in the whole car.... like a big hesitation for half a second then back to normal. Its fine while driving, only when idling.

The damn radiator also cracked right after I did the plugs now I have a slow coolant leak from the very top of the radiator. Can't see where its coming from.

 

The spark plug well tube seals are basically built in to the valve covers and are not an individually replaceable component UNLESS you are willing to. It requires some shenaniganery, you can google search some threads about replacing vq35de spark plug well tube seals and see if it's something you are comfortable doing.

Personally I didn't have any issues with it and $20 for a set of well tube seals, $25 for gaskets, and another $5 for a bottle of Permatex Ultra Grey seemed like the correct route for me.

 

I had the same large misfire for a brief moment on my car as well, but it hasn't done that in a few months. Come to think of it, it hasn't done it since my DIY grounding kit. I've heard that a failing alternator can cause it.
For the radiator, make sure it isn't from one of the hoses leaking. Pressure testers are very helpful with finding leaks.

 

True, that. But note that the OEM plastic radiators are notorious for failing with a crack along the top.

 

Yeah my recommendation would be to replace the valve covers its easy just a little time consuming, also id stay away from the after market/3rd party valve covers for our cars as i was doing research I hear those fail right away or just don't last long and the same issue will happen again. Maybe someone can chime in on there experience but for me i bit my lip and pulled the trigger on oem factory replacements did the job and also used black rtv for extra sealing not sure if it will help but knowing replaced with OEM makes me sleep better, lol!

 

I had the same issue on my G35. I replaced the valve covers with the maxima covers and haven't had any issues since. Took a while to do but I followed a DIY someone posted for the tq specs and everything seems to working fine.