Originally Posted by tommyboy8072002
Well I changed the vss. New Ground wires And still doing it. So I Think I am going to sell it. Or convert it to a 7.3 diesel.
I suggested ground wires on the head because several years ago we built a 351 Ford powered kit Ferrari California Special which uses an MSD ignition system. The owner doesn't like the multiplicity of ground wires and keeps removing them. We've been through a couple, three fried MSD boxes already as a result. He was back a couple months ago with symptoms very similar to yours so I replaced the box and built new head grounds; again! Problem solved for now. So in your case, if it's high voltage getting back into the MSD from a lack of head grounds, the electronics are fried, maybe not out to lunch, but certainly limping.
This is not to say there aren't other causes or contributors that I don't know and can't answer because it isn't my head under your trucks hood.
I will say after having sat unused for some time it could be the injectors or the poppet’s at the end of the injection tubes, the failure of the poppet’s is well documented for the Vortec engine. A cleaner sometimes helps if it's gunk that can be dissolved and washed away, if it isn't or doesn't, the problem will remain. It was suggested that you look at the plugs this can be helpful. Certainly a poppet that's dribbling will show as a fuel wetted plug this can be black carbon to gas wet. A poppet that isn't lifting would probably result in a cylinder not firing or not firing hot enough to keep the plug clean so the plug would most likely be oily wet, maybe a bit fuel wet as well. But this can be a bad cam, lifter or valve as well. A miss firing ignition will probably show wetness on several to all the plugs. A vacuum leak will dry the mixture out make it look lean, one or more of the plugs will be light to white in color where the mixture is lean resulting in a high operating temperature in that cylinder. Keep in mind that checking plugs that are in a failing engine can be deceiving because in many cases the engine can't be run enough to bring it to operating temperature nor put operating loads on it, this will result in the plugs appearing carboned or even wet. It can also lead to conductive paths on the insulator so the plug doesn't perform correctly even though the root cause problem of the engine has been fixed; new plugs would be required in this case. Which is something you’ve already done with no improvement? Not to say it won't need a fresh set again, just pointing this out.