Folks, what causes pre-ignition in a diesel. No, its not nailing, the engine still has some subtle nailing here and there, its pre-ignition ( or maybe post-ignition??) at part throttle. Once above 4000 it runs like a champ, but at mid throttle acceleration, preignition and the engine bucks as it goes through incomplete combustion.

The good news is I;ve been driving it like grandma ( pretending its a 240d!)trying to keep it from rattling = 735 miles on a tank of fuel. BUT , that rattling has/is messing up the alum head for sure. ( hope not the slugs)

Cetane boost is in right now, to see if it helps. Might have to start brewing bio if it does.

Would low fuel pressure cause it?

I've reconnected the EGR as I think it will help mitigate it by upping the inlet air temps. ( backwards from a gasser)

Just trying to understand diesel pre-ignition as opposed to gasser, since gasser is usually bass-ackwards from compression engines. This is like throwing 87 octane in a 10.5:1 gasser.

BTW IP timing is spot on, injectors have been redone, engine has seen Purge.

THNX!