In my experience changing out all the glow plugs, the pre-chamber area where the glow plugs are inserted was badly carboned up. I used a glow plug reamer to clean this out in that immediate area, and it got out a bunch of carbon. Removing the old glow plugs required a lot of care because carbon was caked around then.

So that does lend some weight to the carboned-up prechamber theory.

The effect of some smoke and stumbling on cold startup is not worth it to me to pull the pre-chambers out for cleaning. And I have my doubts that Red-Line can clean this stuff out, but its worth a try.

Ken300D