I can only think that there may be a valve that may be sticking open sometimes. I broke an exhaust rocker arm on a Datsun diesel that I used to have. It happened to me while going to work. It still ran but it was backfiring back into intake. Ran like heck and was real loud but I was still able to limp back home at freeway speeds.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012