Engine: 3.2: p0420 & p0430 on volvo xc90 2012

[alon egozi]

I have a Volvo xc90 2012 3.2.
just found out i probably share the same problem as many other 3.2 owners do: "high oil consumption" and catalytic converter failure (p0420 and p0430 codes). another thing i didn't see anyone wrote about, is about the plugs. mine were covered with white sediment. some mechanics told me that its the burning of oil which comes out of the rings and some mechanics told me its the uneven burning of gas since there is A poor mixture of gas and oxygen. my thoughts are that maybe poor mixture could be since my converters are bad, the o2 sensors are getting bad reading and engine is using poor mixture. does anyone have any opinion on my case?

i attached some pictures if any one can recognise what that is

after reading another thread about high oil consumption i decided i will replace my oil from 5w30 to castrol edge 0w40 as recommended in the thread but not before doing flushing of the engine and putting the oil on a clean engine with new oil filter.
I should say the car is with me for only a year. I bought the car in that situation.
what i did since i bought the car was:
replacing the plugs which started very fast to get this white build up again.
I replaced the pcv 2 weeks ago - a few month after the new plugs.
I renewed the catalytic converters to new ones (not original but by "Magna Flow"), after doing this i resolved the p0420 & p0430 for maybe a month and then it returned again 😭. Since then i am trying to find the root reason of all those problems - those codes, white build up and oil consumption. obviously something is causing this white build up on the plugs and probably it has to do with the oil and the converters.

I looked over the history of xc90 since the last owner.
he did nothing with engine beside replacing the drive-shaft. all the other stuff are maintenance - oils, filters and so on.
the only thing for our matter is that the problem of the p0430&420 started in 2017. from what i understand from the history and from what i recall him telling me, is that he didn't do anything about it.
here is summarized list of what i did since i bought the car:
1) replaced the the spark plugs to Denso 4704 IKH20TT Iridium TT Spark Plug
2) took out the catalytic converters and "transplanted" new convertres made by "magnaflow"
3) replaced to original pcv to vaico pcv
4) replaced the Lambda sensor to Denso DOX-0526
5) flushed the engine
6) replaced the oil to new Castrol EDGE Euro 0W-40 A3/B4 Advanced Full Synthetic Motor Oil.
7) added Restore 8-Cylinder Formula Engine Restorer and Lub

that's all that was done as i know. maybe something was done before 2017 or in a different garage that i dont know of.

since i did the oil change the car still gives the message about the engine but there is no check engine light right now. when i connect my generic computer it gives me the p0430&420 codes.

the car "eats" oil more than it should although its less than it used to be since the oil exchange to castrol 0w40 was done.
of course there is this white stuff on the plugs

and for the information all of the mechanics i talked to except one told me it is probably the Piston ring. the only mechanic who told me it is not is a Volvo pro who told me its because i didn't use original converters when i changed them. he says if there was a real problem with the piston rings i would have seen smoke coming out at least at the morning startup and there is nothing! it's totally clean.
that volvo mechanic told me that white stuff is normal.
about the pcv, i checked there is good vacuum by placing a rubber glove on the oil opening and checking to see it is sucked inside as many suggested to check.

looking for help on this

[TruckbusUK]

Hello, re the plugs .... and this is just my opinion, it does not look like ash deposits to me (not an even coating on the plug,) but I think its more likely to be the mixture is running too lean, or pinking (pre-ignition damage) or the plugs are maybe the wrong type are or you are using a fuel additive that's not agreeing with the setup of the engine.

Just a quick opinion from looking at the picture of the plug.

Hope it helps

[alon egozi]

After those plugs in the picture i put new ones and this white build-up starts again

[alon egozi]

After replacing

[alon egozi]

Anyone?

[Kev0607]

Looks like the fuel mixture is too rich.

Are you using any kind of fuel additive?

Are those spark plugs the correct ones specified by Volvo?

Maybe you need to bring it to the Volvo mechanic to get him to check over it.

[alon egozi]

No fuel additives
I am using the correct plugs
The kind is written up in the thread