4.3 V6 Cylinder Misfires
 

Hey, gang! I'm having an issue with my 2002 S-10 Blazer equipped with a 4.3L Vortec V6. It keeps throwing a code for a Cylinder 3 Misfire and sometimes a Random, Multi-Cylinder Misfire.

We have already replaced the cap, rotor button, plugs and wires, all AC-Delco. The #3 plug was checked since the code didn't go away, after doing the tune-up, to make sure it wasn't damaged while putting it in as it was in an awkward location.

I'm thinking this may be a distributor issue, simply because of the multi-cylinder code. Any thoughts? Thanks!

It wouldnt be a bad idea to replace upstream O2 sensors, a bad sensor on bank 1 was causing me to run rich and have misfires on 1,3 and 5

It could also be the spider injection system as well causing a multiple cylinder misfire.

I had the same problem for about 6 months. Here is what fixed it: Cut the hole in the dist hold down bracket bigger and find out where it runs best. : No more misfire for me :)

Have trouble with # 3 and 5 cylinder also misfiring have it at garage now says it might be spider injector system i was wandering after reading this if the o2 sensor really controls it that much some said replace it is it worth a try

I had 2 Astro vans with the 4.3. (1995 and 1999) Had random misfires no one could figure out. Turned out to be simple, a worn distributor gear. Guess it was a common problem.

O2 fixed mine
 

O2 sensor is worth a try. I had my neighborhood mechanic hook it up to his reader, and we could tell from the numbers that the 2 of the sensors were bad.

What happens with a bad sensor:
-exhaust mix leaving the engine shows bad fuel/oxygen content mix
-computer dumps in extra gas/oxygen into cylinders
-mix worsens, and bad mix either doesn't ignite or ignites poorly

definitely worth a shot if you can afford to put new sensors in. My blazer has 198k miles on it, and i didn't think it would ever run smoothly, but after 2 o2 sensors, she purrs like a kitten

I had the same problem random misfires I bought a better cap and rotor at orileys auto parts that fixed my problem

If all else fails do a compression test, it's free. That is where I found my culprit. Head gasket blown between two cylinders. Ran rough at idle but fairly well while driving it. Good luck.

its worth a try , hundred bucks a pop..