Carbon Buildup

Leesaover

I purchased my 2011 GMC Acadia Denali brand new. It now has 82,000 miles on it and has been diagnosed with major carbon deposits. It started last Winter when my check engine light came on. I took it to my mechanic who said that the codes were for engine misfires and it was due to carbon build up behind the intake valves. They did an induction cleaning (around $400) and I was on my way, everything was fine until the next winter started (December, 2019). I took it back to the same mechanic who told me the same thing he told me last year. He said that it is a major issue with GM motors and not uncommon. He said that GM knows about it and is doing nothing to fix the problem.
He did the same cleaning and told me to use top tier gas and put Sea Foam in my gas tank at every oil change. The light came back on the next time I started it. I called him and he got impatient with me telling me that the issue is not fixable other than doing what he told me to do or taking the engine apart and physically scrubbing it (or something like that). I took it to another mechanic to get a second opinion and he has told me the same thing. Has anyone else had this same problem and were you able to "blow the carbon out" by using Sea Foam? I really love this truck and it has been good to me (except having to replace the alternator twice in one year) since I've owned it.

thecardoc3

Soft carbon deposits can be cleaned up by induction cleaning services, but not always completely removed. Hard carbon deposits require a more agressive service such as walnut shell blasting. To do that the intake manifold needs to be removed. What you have been advised to do so far is accurate and usually works well enough, but does not solve every condition. https://www.youtube.com/watch?v=KFvXbTIiAVY