I may have a dying 4.8L on my hands. It's throwing misfire codes on startup and has an intermitent miss under normal driving conditions. It has a slight hesitation during acceleration but its still making power, especially when the turbo kicks in. Before someone screams #7, I already checked the plug and the compression on that cylinder - it looks good. I'm not consuming oil either so I doubt I busted a ring land. Ideas?
~ Forged engine of some type ~ Ball bearing turbo of an unconfirmed size ~ 4L8000 trans ~ Beefy fuel system ~
Did you check all plugs? What abut wires? What about coils? What about injectors? Did you do a full compression test?
T-RAV99 GMC | 5.3 | Skinny White Guy Tuned
Didn't have time to check all the cylinders, but I will. I honestly never though about ignition components though
~ Forged engine of some type ~ Ball bearing turbo of an unconfirmed size ~ 4L8000 trans ~ Beefy fuel system ~
I have seen many exibit similiar concerns as yours which had valve issues, springs week, as well a few with failing valve seats. It is kinda difficult to diagnose valve seats which are in early stage of failure. I have found it best to pull the valve cover and make sure the rocker hasn't become tight which would indicate the seats are going away. hope thats not the case however I fear otherwise.
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