I have a 99 chevy blazer i hope someone would be able to help.
so far i have changed plugs wires cmp cap rotor ignition module d cap fixed an vacuum leak checked fuel pressure its good.
cleaned battery terminals and checked all grounds less then 01 ohms and i still have. Miss. I checked cylinders 3 and 6 compression is 110. Has 230,000 roughly miles on it. And i put a new catalytic converter on.

It was first a miss on cylinder #6 after i replaced the rotor the miss changed to cylinder #3.

I cant figure this out HELP ANYONE DRIVING ME CRAZY... LOL

 

Welcome to the forum. Misfires can be frustrating but we can get you fixed up.

There are probably at least 2 dozens possibilities. You need to measure compression on all cylinders and look at the spread. You will need to check CMP retard with a capable scanner and make sure that you are within the -2 to +2 spec. Then you can also look at the misfire counters to see what's going on. If you have a fuel pressure gauge, test per the sticky at the top of this forum. Also, run the truck in the dark and mist around all ignition components looking for arching. Pull the 3 and 6 plug wires and see if the spark is as strong and regular as the good cylinders. There's more but this will get you started.

Did you have carbon traces under your old distr cap?

This might help:

https://blazerforum.com/forum/2nd-ge...72/#post732722


George

 

I have been fighting the same P0300 off and on for years. It seems to be a common trait with these 4.3s. Çyl 3 and 6 also on mine get the most misfires.

Best of luck to ya.