specific misfire to random misfire

[Biggumzmcgee]

I'm going to be as complete in my description as possible so as to leave no questions. I was driving my 96 tahoe to work one night with the cruise control set and all of a sudden the check engine light started flashing, the rpm's shot up like a cylinder died, and there was a loud ticking ONLY audible during acceleration. I stopped to check things out and noticed nothing visibly wrong so I did the smart thing called in to work and limped it home. Upon arrival I threw a code reader on it and got P0305, misfire in cylinder 5. Following day I pulled the valve cover off to see if there was anything apparent in there, there was not. It took me a while to acquire the necessary tools to perform a compression test. Upon starting it up to bring it to operating temperature the rough idle was drastically smoothed out-not gone-but drastically smoothed and the loud tick was now almost completely gone, you really gotta strain to hear it. I threw the code reader on again and now got P0300, random cylinder misfire detected. What are some possible things that could cause this? Any help would be greatly appreciated, I'm really stuck on this one. Thanks

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[73shark]

Might check plugs and wires.

Not sure about the ticking sound, could be a lifter? How many miles on the truck?

[Biggumzmcgee]

I bought it off of craigslist and it was advertised as having 26k on a rebuilt motor, judging by the condition of other components on the motor I do believe it's rebuilt but I'm wondering if just the block was rebuilt and the heads just re-used without being reconditioned themselves. Someone recommended that I clean the valve train of carbon/varnish and it should clear up the problem. The plugs and wires are good, I considered that already. Thanks for the input though