Have you pulled your plugs to look at them? If not, that would be the next thing I'd do.

 

I pulled #1 a couple of months ago, fairly clean but they are Autolite plugs so I’m gonna pick up some AC Delco plugs and replace the misfire ones first. More to follow!

 

I don't recommend buying plugs just yet. Pull them and look at them. Compare the plugs on the cylinders that are misfiring with the plugs on the cylinders that are operating normally.

That might tell you a lot.

Its odd that you have 123 grouped like that. We need to figure out what is the common denominator. If they were on the same bank, I'd be thinking head gasket, but they aren't. But look at those plugs may tell us a lot.

But it's not time to be buying parts.

https://angf35eis.com/chevy-4-3-l-3-...-firing-order/

 

Good thinking as I have thrown a ton of parts at this, each part improves just slightly but nothing has cured it completely. I will drive it one day with my new scanner running and try to catch the data when the SES lights up. Last 3/4 drives it takes about 20/30 minutes to throw the code.

 

This is not the solution you are looking for:




Testing is a far better way to find and solve a problem. Firing the parts cannon is expensive and frustrating.

 

all plugs are dry, no oil build up. I thinking it’s running lean? #2 plug wire wasn’t fully connected so that may explain #2 misfire. Will install to different cylinder positions and see if the misfires stay at #1/2 or follow to new cylinder.

 

Drove yesterday, still gets po300. New plugs installed, #2 is the main misfire, up to 90 misfires at a time.

 

Still working the mis fire issue, new plugs helped, data now is showing #1 with just a few 5/7 then zero for a few seconds and repeat. Now#2 seems to be the heavy hitter with up to 96 misfires,pause and start over. I found a misfire history tab that showed #1 at 478. #2 at 359. #3 at31, nothing for #4-5-6. Now what?

 

Yo where did all the people and suggestions go?

 

Blue ridge mark inserted himself here and on a couple of other threads so I let him do his thing to see if we had a new contributor that can help people fix their trucks. If he does not show up today then I’ll jump back in to help you.

How is it running?

George