first time posting so hi everyone. As the title says it knocks it squels and has miss and is making bad power. was told burnt valve but i dont know. Did find a youtube on a blazer doing pretty much the exact same thing i can link but they dont go on to say what the problem is. heres the link and any help would be appreciated.
http://www.youtube.com/watch?v=pRIXKEFMtvM again not mine my son broke my camera but it sounds pretty much the same

 

is it possible on mine that its a bad balance shaft?

 

sounds to be on the passenger side top to middle of the block...Kind of hoping it is the balance shaft bearing gone out for the squelling and allowing the shaft to bounce around for the knocking...still a pain in the *** to replace but shouldn't cost me a motor. Apparently they have a habit of going out but all the videos i have found of engines with bad balance shafts they are already pulled out and are going through it and showing the noise it makes when the shake it back and forth by hand. Hard to be like oh thats my noise when the isn't running but it does sound awful lot alike. I pulled the valve cover on the passenger side (freaking chore and a half) and the checked the valves and had the woman crank it over and they seem to operate normally


forgot to add that my oil pressure on it stays in the good range hot or cold also. It does have a bad loss of power also almost like the timing is way retarded but it starts up fine. While pulling plug wires to see if the knock would stop (little v6 will shock the bejesus out of you) the noise wouldn't go away and on almost every plug when i removed the wire it would die and i would have to start it up again with the wire off to hear it run.

 

how about if i pull the gear that drives the balance shaft and pull the shaft out to eliminate it?

 

Gosh This is a strange one. Hopefully somebody will know what's up.
Anywho I would advise against eliminating the Balance shaft because a 90* V6 isn't harmonically balanced. You'll get a loping rhythm.

 

Might not be your problem, but the bearing in the distributor on my Bravada essentially seized up (very, very hard to turn by hand when we pulled it) and it squealed really bad. Caused a miss, too.

 

I tore the intake off today (dizzy turns fine) checked the balance shaft and while there was front to back play it was small enough i just wrote it off as normal. I did run it for a few seconds with no belt on and that seemed to get rid of the squeal (may just be coincidence that it wasn't doing for the 10 seconds or so i ran it with no belt on). Gonna go ahead and pull the heads tomorrow depending on weather and go from there. Really hope its not in the rods/mains since i don't have a engine lift to pull it and go through the bottom end.

 

I know this is an old post but mine is doing the exact same thing. Squeals like a banshee and is shaking wildly. I'm new to the 4.3 and I'm at a loss! Did you ever find out what was causing this? I checked my dizzy and its fine. No water in the cylinders, all plugs clean and firing. Any help would be appreciated.

 

try to find the knock senors on the motor. I know one of them is behind the distrubitor on the back of the motor. The other is located on the on the side of the motor. Replacing should clear up your problem