Originally Posted By: MGregoir
This is interesting.
1. Oil does not come in contact with intake valves so there is no oil that should be able to clean up intake valve deposits.
2. Fuel does not come in contact with intake valves so I can't see them building up much in the way of back-side deposits, and nothing put in the fuel will "clean up" deposits on them either.
3. The only thing the intake valves are handling is air on the stem side and then the combustion chamber on the other side. The way to get cleaner into that area would probably be SeaFoam sucked in through a vacuum line or sprayed in the air intake to clean the combustion chambers.
Other than that...I think your intake valves are more than just figuratively high and dry.
There has to be oil passing down the valve stems, or the guides will wear out/stems sieze in short order. The amount might be miniscule, but over time, there will be significant migration.
Another source could be PCV, and EGR.
Depending on the exact point of injection timing, there could be some fuel reversion at various operating regimes.
As to getting rid of them ????
water rinse, or one of those other feed through additives (not for diesels 'though.