Hi guys,for about 1 month the car started running poorly.The engine shakes very bad in lower revs but if i accelerate it would start running ok.I put the tester and it got missfire on cylinder 5.After seeing that i went with the car to a mechanic to change the spark plugs.When changing the spark plugs we saw that the spark plugs we;re full of oil.What does that mean?Is it very bad?He told me we should change the gasked or something like that.
The car is a 400h

 

You said "the spark plugS were full of oil", you only have one spark plug in that cylinder... were there multiple plugs with oil found on them OR just cylinder #5? The rest of your post is pretty much void of information needed to make a decent assessment but here goes... was the oil on the spark plug end that goes in the engine OR on the outside where the socket wrench goes? Huge difference and all-important to know. CAn you prvide pcs? IF the oil was where the spark originates, inside the engine, then you're very likely requiring a complete engine rebuild, if it is only on the outside then it is likely only a cheap gasket

 

Hi,all the 3 of them from the back we're full of oil.I guess the oil was on the outside where the socked wrech goes.

 

If thats the case, Then you'll need to get a v/c kit which comes w/ the oil seals. Kinda surprised that your mechanic, came to the conclution that you need to rebuild the motor for w/o looking at the plugs.......

 

Guessing won't help unles you just want guesses to fix things... might you have any pics of the oily plugs? In order to give any suggestions we'll need to be sure whether it is on the outside or inside of engine.

Again = inside of engine means a total rebuild but if it is more than a single plug, you said a bank or 3 of them, it does not sounds like a ring failed rather just your valve cover gasket leaking.
Outside of engine (oil only on the portion that is external of engine, probably a valve cover gasket and a cheap easy fix for the front bank of cylinders but you said it is the rear bank so he likely has a lot of stuff apart in order to access those back plugs so still an easy and cheap fix since he has it apart already. To get to the back plugs to diagnose takes a bit of time.

Spark plug tubes, valve cover gasket, PCV valve since you're back there, and all 6 spark plugs with OEM or NGK equivalents and you're good. If he has the back apart this is a very simple and cheap fix

 

That's Great Advice-5☆