Hello everyone

I have a 2012 XJL 5.0 supercharged, I have an issue with white smoke coming from exhaust on idle. And there is a little gas smell in the oil

I took the car to 3 mechanic. None of them seem to know what’s going on. I changed PCV value cover and I know it’s not a head gasket issue, there is no coolant lose or overheating.

what could be the issue?

 

Mxjl, lets break this down to 2 issues (white smoke and gas in the oil). This may help to understand what you have going on.

First, the gas in the oil. This can be caused by a few things. The more unlikely based on age is the fact that you have worn out rings (would only likely to be true if you have like 250K miles on the engine). At that point, the engine is simply worn out and would need a rebuild. The more likely situation is you have a fuel injector (or two) that are starting to go that are over feeding a cylinder (or two) and this is causing blowby of the rings, leading to gas build up in the fuel. This is a known issue with the engine. You can try getting either a fuel system cleaning at a professional shop (probably run you about $300) or you can try changing up the fuel you use. What I mean by this is if you use the same brand all the time (lets say Shell), run a tank or two of another quality brand (say, Sunoco). With this, put in a bottle or two of fuel injector cleaner. See what you have then. Running a different brand of gasoline works on the principle that each manufacturer of gas has "their blend" of detergents. No brand gets 100% of the gunk. So, by switching to a different brand, they are going to use different products which hopefully will catch what your normal product misses.

Now, for the smoke issue. I would say that most likely what you are experiencing is nothing more than a changing of the seasons and normal exhaust. What I mean by this is that as temperatures fall, your hot exhaust contains a fair amount of water (what gasoline in theory burns to). So, as this hits the colder air, you are seeing the steam condense to water as it leaves the tailpipe. This could be interpreted as smoke. Now, if the smoke has a gray tint to it, then you may be experiencing some oil burning and this would be more of a normal thing for an older engine. I would keep an eye on the oil. This is where I would say a compression test of the engine would be called for. In this case, you should be more interested in seeing that all cylinders are within 10% of each other than the value of the compression. Yes, the second number is important, but, with wear in the engine, it is possible it is not going ot be up where everyone wants it. So, if you measure all 8 and they all fall in the 140-155 psig range, then I would call that good. I would be worried if I had 7 cylinders in the 160-170 psig range and one down at 60 psig. That 60 psig cylinder has some issue that needs to be resolved.

 

If this symptom presents on a cold start only, it's normal. Fueling is enriched on a cold start to warm up the catalytic converters more quickly for emissions purposes. Rich condition AFTER warm up as mentioned above may be a stuck open injector. Test your fuel pressure with the engine off. Your fuel rail should hold full pressure almost indefinitely. If not, there's a leak or your injector is leaking down into the cylinder which would also cause a fuel smell in the oil,

 

It would be helpful to know how many kilometres/miles are showing on the instrument cluster, and if there are any DTCs stored.

Fuel in the oil and excessive smoking from the exhaust are usually indicative of a sticking or failed fuel injector. Fuel in the engine oil can eventually lead to main and or rod bearing failure.