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A Nissan mechanic told me once that short trips are bad for these engines. Never get warm enough. These cars need to be driven.

She has a 76 with the lower energy ignition system. You might be thinking of 78 and on. Spec. for 76 is actually .031 - .035" so it was on the high end. I looked back through the original thread but can't find anything about miles on the engine. My 76 had high miles and worn valve seals and burned some oil at high RPM. Those plugs seem pretty black and the fact the engine ran very well but you still ended up with black, wet plugs, after just a few miles with the new plugs seems to indicate some oil leakage in tot he cylinders. I can't recall much at all either, about the general state of the car when received. Maybe it's a high mile car that sat, or a low mile car that sat, or a high mile car that was a daily driver. The first two could cause a little rust in the cylinders that might wear in to shape, the last would mean it just is the way it is. Someone mentioned Italian tune-up a while ago, I think. Maybe it just needs some good road runs to settle down. The daily warm-ups and mail box trips though, might not be enough to keep it in good shape. They like to run.

sure looks like it's running rich + getting some oil worn/dried-out valve guide seals will suck oil into the chambers during deceleration (vacuum conditions) causing a surprising amount of oil burn. they are cheap (less than $20 IIRC) and not tough to install. you get a free valve lash adjust out of the deal as well i've replaced a couple sets and the results have been noticeable. everything i've read says not to run an L6 below 2K revs as it will carbon up. i don't believe 4K is "pushing it" - that's a basic shift point. rev it up to 5K regularly, it's meant designed for it. just gotta re-calibrate the brain from old american iron...

I have never used the potentiometer trick so I'm not sure, but Siteunseen, Fastwoman and others on the site have used it with success to compensate for aging ECU's. What was referred to as a redneck tuneup or a Italian tuneup, sure, blowing out the carbon every once in a while won't hurt.

Ah, the lower energy ignition system...forgot about that. Thanks for the refresher Greg. For some reason I keep thinking 77 instead of 76.

I appreciate the votes of confidence It's a balancing act for sure. I've fallen victim to the "well, while I'm at it, I guess I can take care of this too..." and then the whole dang thing is in pieces across the garage (and office) floors!