1997 k1500 5.7 Vortec P0307 misfire

[1997-Z71]

As the title states it is a 1997 k1500 with the vortec 350. I did a full tune up a couple years ago and only driven around 1000 miles since, trans went out and needed rebuilt. I also replaced all intake manifold gaskets and upgraded the injection from poppets to the mpfi that I believe was ac delco brand. So 2 years and at least 1000 miles later the trans is rebuilt and installed and I started driving her again. All was fine the first few days then the cel started flashing. This only occurs after the truck reaches operating temp and is shut off and restarted after a short time. If I let the truck sit and clear the code it drives like a dream until I shut her off when warm and restart shortly after. I am about to subscribe to Alldata to gain access to the diagnostics procedure for this code and wanted to see if anyone else has had this happen? I will swap plug wires later today and check the cylinder 7 plug, but I am not expecting to find anything since they are practically brand new. Any info will be appreciated, oh and my driving style is pretty laid back, no fast acceleration or sudden stops, (new insurance company monitoring driving habits). Thanks in advance

 

[1997-Z71]

Quick note, I had another distributor cap and swapped it, she ran fine for a half hour or so and restarted a couple times without issue, parked it overnight then went to emissions first thing and passed, then I went to the store and when I came back i started the truck and felt the chugging happening again, and sure enough cel started flashing a couple minutes later and it was code P0307 again but at least I got through emissions so I have time to repair now, but I won't drive her with a misfire until I have at least attempted a repair and test drive to verify but this one has been a little tricky

 

[SilverFatBoy]

This might be a long shot, but when my 97 Tahoe kept throwing a P0307 code, I tried EVERYTHING (Including taking it to a Chevrolet dealer). When none of that fixed the problem, I went searching on the internet. A couple of people said that their distributor driven gear (cam position sensor) was worn, I pulled my out & discovered that the teeth on one side only, were worn to a knife edge (even cut my finger it was so sharp). As i had purchased an extended warranty, I took the dist back to the dealer & asked them if this could be the problem? The tech was embarrassed, as he wanted to blame "Non Delco/ GM parts" for the misfire code. Once that was replaced (with a genuine AC Delco plastic part), I've had no problems with misfires.

 

[1997-Z71]

SilverFatBoy thank you for the response, I have been wanting to replace my distributor anyway since one of the plastic threaded tabs broke a while back, I have been using a machine screw and nut to hold the cap in place for a few years now. I will probably upgrade to an all metal distributor.