Uneven extrusion. Please help!

I’ve been printing succesfully for a while now on the mini but recently started running into a new issue.

A few prints had dark ‘chunks’ and some obvious under-extrusion all around the same height (was a multi part print of the same model). I’ve printed the model multiple times in the past with no issues, using all the same settings, and multiple different filaments.

I tested the extruder by lifting it up and doing a 100mm extrusion through Octoprint, the filament will come out normally for a second and then start to curve and curl, I’ll see thin sections. I was seeing little ‘chunks’ of what looked like burned filament or something, not entirely sure what it was.

I did a couple of cold pulls and things looked normal as far as what was coming out of the printer when I did the cold pull, tested the extrusion again and it’s still doing the same thing but now, without the chunks. Just seems to extrude very inconsistently.

Next step, I cleaned the knurled gear that drives the filament really well, did a couple more cold pulls, and just extruded a bunch of filament out (about 700mm). I tweaked the tension on the little idler arm doodad as well.

Next test: I marked some natural ABS with a marker and watched the mark move as it was trying to extrude. The mark moves, stutters, moves, stops, moves, slows down, moves, etc. All during 1 300mm extrusion (just extruding filament, not printing, I know the feed rate changes during a print).

I’m still seeing the filament curl as soon as it comes out of the nozzle and seeing normal extrusion followed by obviously thin extrusion, all seemingly random. I’ve tried tweaking the tension from way too loose, to way too tight, I’ve tried turning the temperature both up and down on the extruder, I’ve even run some gauged wire through the nozzle in both directions ot try and clean out hte little hole under the impression that the nozzle hole is no longer perfectly round or something. I’m at a loss, it’ll print fine for a little bit and then you’ll see obvious signs of under-extrusion.

software wise, I’ve measured the filament, tried multiple filaments, adjusted the extrusion rate, adjusted the software defined filament size to match the specific filament I’m running, etc.

I feel like I’m missing something obvious here… please help.

Just throwing it out there…
Is the mini fan running?

My filament doesn’t always extrude straight down when manually extruding either. If I were to guess, is that it usually curls up when the head is really hot(239’ish)…

I have had issues with the machine starting to over-extrude recently… But thanks to a fellow user, I overcame it by lowering the feed to 90% as per his suggestion…

The tensioner has caused me some bad prints, but mainly at the beginning of a print, as it was too loose.

I’ve been printing with
3mm ABS

3mm HIPS

3mm T-Glass