That noise you described sounds exactly like my issue! Must be raw fuel igniting in the exhaust cause the sound is coming directly from the pipe in between CAT and muffler not from engine also when I revved it the noise stopped. I also have p0304 it happened right after I replaced the fuel filter (mine is early gen 2003 so it has one) and the fuel pressure regulator.
Excellent video. Thank you again for showing the work you continue to put into the Envoy. I am thinking about doing a replacing of all of the coil packs as well as doing a new/higher performance air flow along with getting a performance chip to increase fuel efficiency. Looking for an opinion on doing such thing.
Thank you. I don't have any experience with performance upgrades, but check around the forums. I'm sure a lot of guys have done what you're looking to do.
Hey bud I have/had the same issue running ugly I changed the 6 spark plugs then 1coil waiting for the new one to come in. now it won’t start it cranks but won’t start I think I put the plug in to the new coil backwards causing a new problem I don’t know where to start it’s cranking but not starting now
