bradland

99 LS400 - 190,000 miles
Start driving last Sun afternoon and idle is rough, doesn't go away, check engine light comes on and STARTS FLASHING!!! I've never seen the CE light flash before! So I pull in to Autozone (quick disclaimer- I don't buy parts from them but they will check trouble codes for you...) Turns out cylinder No. 8 is not firing so lets assume a bad coil. My assumption was correct. While I was at AZ I bought 8 NGK 4589 plugs. They had a Duralast coil but I prefer to stay far away from EVERYTHING Duralast! Ordered a Delphi coil on Amazon which quickly arrived Tuesday but I did have to drive the car a little, approx 30 miles roundtrip to work, before I could replace the bad coil.

Tuesday evening I replace the coil on cylinder No. 8 and of course a new plug. Rough idle is gone and everything seems fine... Now that I know I've fixed the issue it's time to replace the remaining 7 plugs. The last time I did this was around 105,xxx miles. Obviously a bit over due but not too bad until I got to cylinders No. 3 and 4. No. 3 smelled of oil and had dirty residue on the plug boot, No. 4 however was completely oil fouled literally dripping oil. Cylinders 3 and 4 are adjacent to each other, 2nd from the front No 3 on the drivers side No 4 on the passenger side.

My question...?
Would one cylinder not firing create a situation to oil foul the spark plug of another cylinder?

Legender

I don't think so. These cylinders are sealed off from each other. The common thread between them is the valve cover gasket. When was the last time it was replaced? I suspect you've got leaky tube seals and leaky valve cover gaskets that are causing oil to seep into the cylinders and coat the plugs. I'd check that first.

sha4000

iTrader: (1)

^^^^^^ I agree.

PureDrifter

iTrader: (10)

The valve cover gasket won't cause oil to leak into the cylinders, but the spark plug tube gaskets failing will. It's a bit of labor but not too bad to replace it all.

sha4000

iTrader: (1)

If your doing tube seals you better change the valve cover gasket too.

dicer

Not good on the catalytic converters, due to the cost and everything else, I would have missed a day of work.

bradland

Thanks for the replies gentlemen! I'm picking up the plug seals and VC gaskets tomorrow AM. Hopefully I'll get them put in by this weekend.

Now I'm wondering if the Coil going bad is in anyway related to the oil leaking around the plug???

PureDrifter

iTrader: (10)

I thought you said it was a different coil that went bad, not the one that had the leaking seal?


Don't forget that you will need a tube of toyota FIPG Black to seal around the edges as shown in the FSM. Permatex Ultra Black should work as well.

Legender

And there is a trick to removing and replacing the tube seals. IIRC, they only go one way so don't force them.

bradland

PureDrifter you are exactly right the No.8 coil was replaced. The No.4 seal is obviously leaking.

BUT... I pulled the #8 plug knowing it was the culprit and didn't think twice about how it looked as I expected it to be in shambles. It was wet and black but I thought that to be normal considering the circumstances. When changing the remaining 7 I didn't expect them to be soaking wet. No.4 stood out and obviously caught my attention...

I'll know for sure when I change the seals but now I suspect #8 may be leaking as well which destroyed the coil???

djamps

Oil leaking into the coil boot can lead to failure. I've seen it happen on Nissan motors (VQ35's are notorious for this same issue). Fortunately on a 1UZ you can replace the seals but on VQ's you have to replace the whole covers.

bradland

Well it's done! Pretty straight forward with the exception of removing the old seals. WOW what a pain in the A$$ that was. Going into this I had read where the seals were hammered out and back in. WRONG for '99's!!! The old seals were so cooked they basically break out in pieces but there are tabs that must be pried up in order to remove them. Then bent back down once the new seals are in. Legender chimed in with the most useful info regarding re orientation (or direction) of the seals and I still got it wrong the first time!!!

I was amazed at how loose the VC bolts were! Also my Snap On 10mm universal socket is my new best friend for those hard to reach VC bolts...

djamps

Good work. it really isn't surprising that the valve cover bolts become loose -- remember the gasket is basically getting flattened out over the years . I've been procrastinating on the valve cover gaskets due to the amount of time it takes someone like me to tackle all the stuff in the way without breaking everything.

Legender

Congrats on getting the new seals and glad we could provide some insight. And yes, the right tools can turn a nightmare task into a normal task. I have not done it myself but read up on it. I just turned mine into the local independent Lexus shop and had it done. Thanks for following up. Hope that corrects all your oil seepage.

YODAONE

Don't forget to order the self-sealing washers/grommets that are used on valve -cover bolts... mind Lexus torque specs.

You can purchase as a bolt/sealing washer assembly or just self-sealing washers.They are a hassle to remove so if a few cents are not an issue buy the aassembly. Ask dealer for number required and acquire a spare in case you drop one....