did tune up on 99 tahoe now has random p0300 misfire code

[big mark]

i did a tune up on my 99 tahoe ,replaced plugs rotor ,cap, plug wire had been 5 years and 40 k miles have replaced fuel filter at last oil change running fine before tune up i probably need to clean o2 sensors also had no misfire befroe just did a tune up.

[jimlem]

Same happened to me. Evidently most SP wires, including OEM are very fragile and crack (nothing visible) but leak easily. Easiest way to check is pull in dark garage or wait til dark out. Start truck, and look under hood and if you get a lightning show like I did, you'll know it is the wires. Just replace them all. Try and after market made of soft silicone.