Automotive VIDEO: Carbon Deposits On Direct Injection Engines Jon Nelson explains why carbon deposits happen and how to diagnose misfires and clean intake valves. Advertisement ByJon Nelson on Dec 5, 2016 AdvertisementClick Here to Read MoreAdvertisement Jon Nelson explains why carbon deposits happen and how to diagnose misfires and clean intake valves. Video courtesy Underhood Service. Advertisement In this article:carbon deposits, engine, intake valve Click to comment Loading Post... Loading Post... Loading Post... Advertisement WEBINARS Watch a webinar for free on-demand! VIDEO Watch the latest video from Tomorrow's Technician. SUBSCRIBE Stay up to date with the latest Tomorrow's Tech news.