Carbon deposits on the EGR are quite common and are simply a byproduct of exhaust gases from the combustion chamber. The higher the mileage, the more likely you are to have this problem. Some fuel additives such as SeaFoam can be mixed with the fuel to help keep the combustion cleaner and in some extreme cases; the product can be supplied directly through a vacuum line straight into the intake manifold. Most additives include instructions for this procedure if applicable.
I use Lucas fuel system additive about every fourth tank of gas and hope that it is doing it’s job; however, you never know until you pull the intake, or heads and take a look at the combustion chambers, or intake side of the valves. In addition, I have been using Amosoil 10W40 synthetic racing oil for the last year and have noticed less oil consumption & carbon build-up on the EGR than with other oils. (Including Mobile-1)
Normally, the EGR should be removed & cleaned as part of routing maintenance, but not many people want to do that, because it is out of site & out of mind until they get a DTC. I remove mine & clean it every 6-months, whether it needs it or not! It only takes a few minutes to remove, clean & lubricate, so it’s a worthwhile maintenance function for me. Nothing is more aggravating, than to be out on the open road and get an EGR DTC. BTW, I still have the OEM EGR @ 133K & it is as clean as a new one inside.
