Stopped by the dealer today. They took heads off yesterday and said the valves were carboned right up. He said they are just putting the heads back on and it would be ready tomorrow.

 

Definitely wanted to see the carbon build purported to be causing this problem.

 

Ummm.....so what's the repair. Are they saying that carbon buildup is causing the problem?

 

The repair was they cleaned the carbon off the valves

 

Yep, I'm disappointed that we don't have any empirical evidence of what the dealer actually did and even more so that we still don't know if the issue persists.

 

That's exactly what I'm thinking

 

The service manager to be more specific said the exhaust valves were particularly carboned up. Correct me if I'm wrong but your egr valve opens when the engine is WOT allowing the intake vacuum to suck exhaust in order to dilute air/fuel mixture and prevent knock. So wouldn't a carboned up exhaust valve restrict flow through the exhaust and egr reducing the egr's effectiveness. Makes sense to me as all my knocking was under heavy load or WOT. As far as not having proof I never thought to ask the manager to take pictures for me as I trusted they knew what they were doing and am confident that when I pick my jeep up tomorrow it won't be knocking.

 

Haha you would be my hero

 

If there is enough carbon on the exhaust valves it can begin to start heating up (possibly keeping valves partially open under load/higher rpm) but more likely is that the EGR valve has as much build up as the valves did. A clogged EGR can cause the issues mentioned, but the bigger question to be answered is why on a relatively new vehicle that the carbon buildup problem exists. I'd still want to see what the EGR valve looked like and I would still be concerned about exhaust velocity with a 3" pipe. If it's not scavenging the cylinders properly the rest of the system isn't working as it should.

 

The issue isn't your trust in the service manager, but providing something above hearsay and myth about the source or a solution.