Hello.

I would like to ask your opinion about the possible theoretical causes of engine failure in my 4x4 YB Sierra.

The photo below shows the damage to the piston on the 3rd cylinder.



At the time of the failure, the engine done about 315,000 km and it was rather outworn (burned 0.5L of oil for every 400km normal driving) There were no modifications. The oil was Motul 300V 15W50. I've been using Denso IK24 sparkplugs. (on the third cylinder the electrode was melted) I did not hear any knocking from the engine just before the failure.
At the moment the engine was rebuilt: skimmed head, new valves, bearings, new pistons, rings etc. (also new fuel pump and fuel filter)
Injectors (blue Weber IW-044) have also been tested, their flow rate and efficiency of solenoid valves is basically almost identical. Electrical connections for fuel pump, injector plugs are clean. The other pistons were not damaged in any way. They have a small spray of carbon deposits.
Question:

What could have caused this type of damage? What should I pay attention to not to repeat the such "entertainment"? What else to check?

Thank you in advance for any suggestions.

 

.....had the same issue with those plugs...yet i was luckier than you..since than 071c....btw check also injector on that cylinder just to make sure that it works.but i believe it works fine..

 

... or maybe the Denso IK24 is the wrong choice for the std. cossie?

 

Nothing wrong with the plug choice. You are burning too much oil I have seen a engine melt like that because of it and everything else was fine.

Mark

 

What octane fuel are you running? Is the fuel older than 6 months?

 

I mainly use Pb98. It may happen that one time I have fueled Pb95. I do not remember at this moment. I always try to avoid the "no name" gas pumps. I did a trip around the country (in total around 900km for two days). Average speed 100 - 140km / h. During the return, when I was already close to home, I accelerated to about 190km/h (the car did not want to go faster). Driving at 190km/h did not last longer than 1 maybe 2km. At this speed, I suddenly saw white smoke in the mirror. I stopped immediately.
(I also gave the turbocharger to the workshop for a rebuild, but they said it's okay.)

 

programm is good ?what air fuel ratio ?

 

I have had the same problem 2 months ago also at cilinder 3. Not as bad as you but still it needs a full rebuild. Als never did had any problems and motor ran fine. Untill head gasket let go. It turned out that it was an injector with was contaminated and therefor sprayed less fuel.