Im hoping for some suggestions guys. I have a 2004 5.4, auto, 4X4 in my truck. When I purchased it, the previous owner told me he had replaced the cam phazers in 2012 and the timing chains, tensioners, guides,oil pump, and gaskets in 2016. It has recently started misfiring again. It runs great right up to where it shifts into final gear. As soon as it shifts, it starts misfiring. I have a scan tool on it and am watching the timing and I have 20-34 degrees advance until it shifts. Once it shifts, the timing drops back to 6-10 degrees, and I believe that is causing the misfire. Once, since this started happening, I could swear it did a misfire burp as it was shifting from 3-4 but not positive and it hasnt happened again. Is there anything else I could be watching on my scan tool that might help? It doesnt have the "diesel" noise in the timing chains of a bad phazer. I may change plugs to rule them out but they shouldnt affect timing that much should they? Have any suggestion, where to look, what else to check? The shifting/timing relationship has me stumped.
Thanks for any suggestions.

 

Go with the easiest/cheapest to start. Do the plugs and boots first. Typical for that same high-gear misfire especially under load. Work to the harder stuff from there if you need to.

 

Using mode 6, find which cylinder is missing and troubleshoot it. Take the plug from the cyl that's missing and swap it with another cyl. Take the coil on the cyl that's missing and swap it with another cyl (not the same cyl you swapped plugs). Drive the truck and see if the miss follows the coil or sparkplug. If it does, you know what is bad

Or start fresh and do a full plug/coil replacement.