Hi, I've got a v6, 99 Chevy Blazer 4wd that has an issue when wet. You see, just this past winter, I had the fuel pump replaced and it ran perfect. When the weather warmed up enough to produce condensation and rain, it would sputter really bad when I started it, but if I let it warm up long enough, it was ok. Now it's been raining constantly, and it's still doing it, so decided to change the plugs and wires, it's been ages anyway, and there definitely was a chance. The warm up time for the idle dropped, which is good, but again, if it sat too long or got wet, it would start REALLY HARD, like I want to die hard, but I'll keep going, and it does, warms up nice after that, but still sputters. Next culprit, possible water in the gas. Lost my cap some time ago, so got a new one, ran the gas till almost empty, using premium gas and heet, ran fine, rained today, hard start and sputter 🙄 About to just blow the thing up, lol, but it's a reliable car, for the most part. Unfortunately, here's another "I'm not really a car guy" lol I know some basics, and can follow directions pretty easy if anyone has any ideas on what to do next.

 

Hi! Welcome. Seems your love/hate relationship with Blazer has begun. 🙂

As to your issue... Moisture in the cap?

 

I 2nd that ^. Another thing you can do when it's dry is start the blazer up and start spraying different suspect parts with a spray bottle like the distributor cap, wires, plugs, etc.

 

Replace the cap and rotor. That fixed my same issues. There are is no seal in the cap so it can build up moisture inside.