Excessive carbon buildup

[ConnieGallas]

I got a code referring to my IAC valve, so I removed it for cleaning. And boy, it sure was dirty.which led me to see how it got so dirty.after looking inside my intake manifold thru the throttle plate,I can't believe the amount of carbon build up. Now what I want to know is, what causes this build up and how can I reduce or eliminate it?

 

[cbxer55]

The EGR valve. It introduces exhaust gas into the manifold. MIne's removed on both my 98 Ranger and my 04 Lightning. No more dirty intakes on either.

 

[Dirtman]

First culprit is the PCV valve which is always an overlooked maintenance item. Once they get dirty and stuck the crankcase pressure starts blowing backwards out of the fresh air side of the system and you are constantly shooting sludge through the throttle body and intake.