The other day I won the lottery at work. Yeah, you heard that right... I got chosen to work on a 2005 F150 equipped with a 5.4L 3valve engine with approximately 170K miles.
Customer complaint was lack of power and dies after about 10 minutes. I go and drive it and sure enough it has no power and is back firing through the intake. I hook up IDS and I see all four cylinders misfiring on that one bank. Because of the symptoms, it was a pretty easy diagnosis. A clogged converter on bank two. I sell it to the customer and explain that we likely have a misfiring plug/coil that will need to be addressed after we replace the converter. I install it - the truck runs well, makes plenty of power, but the valve train is noisy when hot. Downright scary.
After some diagnostics, it becomes apparent the problem lies within the variable cam timing. A simple oil pressure tests reveals a base engine oil pressure hot at idle only hitting 23psi. We rip the front of the engine apart, the oil pan off, and replace all the timing components and oil pump. You should have seen the oil sludge built up throughout this entire engine. It took forever to clean the valve covers and front cover by hand. There was literally an inch thick of oil sludge build up everywhere. We also sold the guy 8 new spark plugs as they were original and because of the horrible process of changing them he decided it was best for us to do it. Another fixed vehicle on the road. Alright!