Reoccuring Misfire code on 4.3 Vortec

[gmoutdoorsman]

I replaced my lower intake gaskets a few months back,also threw in a NEW distributor,cap,and rotor,New Ac Delco Plugs.Engine has a minor hesitation around a certain RPM(only Under Part throttle)Mostly around the shift points.It keeps throwing up a P0300 for Random Misfire.Thinking its the cheap 2 year old plug wires. i did spray silicone sealant around the wires to see if it helped the issue.Didnt seem to help(but i couldnt get the spray 100% around each wire without removing them) Was told by multiple people itd probably need new AC Delco wires. Checked all the injectors and lines/Poppets.No fuel leaks. Think Wires will fix it? atleast couldnt help by any means

 

[iggyspred]

I've got a similar problem as well, p0300, except there are no signs of any misfires other than the code popping up. The SES only shows on long trips, typically going up a mountain. Still trying to sort it out, but here's what I've gathered from my research.

Start with wires. They're inexpensive and it couldn't hurt. Also, check what you replaced; make sure your plugs are seated well, sometimes the little tab on the rotor doesn't contact the cap well, give it a slight bend upward. Spray some ether/carb cleaner/ brake cleaner around the gaskets you replaced checking for vacuum leaks. If there is a tiny bit of slop in the dizzy it will throw the code. There are two vacuum solenoids that mount on the right (pass) side of the intake check those plugs as well as the coil plug. Leaning in over all that to do the dizzy could have split the insulation on a stiff wire causing it to short. O2 sensors can sometimes cause a p0300. Good luck!

 

[skylark]

Have you done a compression check?

 

[gmoutdoorsman]

no I have not. its on my list tho

 

[skylark]

I chased my tail for way too much money several years ago on a p0300. Every thing I did was an improvement but ultimately a cyl had 135# when the others had 180#.