2004 silverado 5.3 misfire when it rains

SOURCE: 2000 chevy silverado cylinder 2 is misfiring

Hello there, I would start by removing the plug from cylinder #2 and check it condtion, I would then verify that spark is or is not getting to that cylinder. If spark is present and the plug looks good, turn the engine over and verify both of these with the plug laying on the valve cover. So if coil is good and plug is good, then it leaves fuel or fuel control issue. A faulty or clogged injector could cause this issue. Let me know how you make out, I'd be glad to assit you farther if need be. Thank you for using fixya.com

SOURCE: 99 chev silverado 4.3L hesitation

After speaking with a couple mechanics and doing some research of my own I found that if your engine still hesitates even after a good tune-up then odds are it’s your Oxygen Sensor(s) or in rare cases your mass air flow sensor. My check engine light never came on though, except a couple times when I washed my undercarriage, which caused my engine to hesitate even stronger but would go away in about 2 days; I guess after everything dried out. I’m changing all four of them, its time anyway; apparently they only last for about 60K miles and I’m pushing 104K. Not sure if this will help anyone else but good luck!

SOURCE: Only when it rains, I get an engine misfire and the check

i had the same problem with my truck...(i have a 99 silverado 4.3L also) i took off the cap, cleaned all of the electrical areas on the inside of the cap and rotor....and put a small thin layor of die electric grease on it all....then before i put the cap back on...i ran a bead of silicone around the cap surface that seats to the distributor...and i havent had a problem for the month that i have done that......hope this helps!

SOURCE: Check Engine Light / Misfiring

if you can drive it to autozone they will read the code for free and tell you what it is

SOURCE: Engine code: Misfire cylinder 1. Replaced plugs

There should be no built up fuel or oil in cylinder. The fuel will be burned off immediately, and there should have been very little unless you have a leaking injector. The only way oil will enter the cylinder is if you have a mechanical failure like worn rings or leaking valve seals.If after replacing the plugs and wires did not correct all or the skip after the first start up and road test then you have another issue causing the skip