Ender 3 pro extruder skipping steps, tried multiple things I've already asked this question somewhere else but unfortunately I had little luck.

So... my Ender 3 Pro extruder just started skipping steps, as in the gears (and the gear pinion) will rotate but the filament won't flow. It all started when I changed PLA filament to a new roll; I thought it might have been the roll faulty so I've tried a spool that had been working fine until 2 hours before it all started. Nope, skipping with that one as well.

Here's what I've tried doing so far:


Replaced the stock PTFE tubing with Capricorn tubing.
Checked that the tubing is tight and does not have play.
Replaced the whole extruder system (except for the extruder motor) with a metal Creality system.
Performed various cold pulls.
Replaced the nozzle.
Upped the extruding temperature from 195&nbsp;°C to 205&nbsp;°C.
Checked that there's the correct distance between the bed and the nozzle.
Yelled at the printer.
Asked for advice to my cats.


None of the above worked, and my cats looked funny at me. Print settings as below:


Filament diameter in the slicer 1.75mm (yes I've checked).
Temperature: 195&nbsp;°C, upped to 205&nbsp;°C.
Print speed: from 20&nbsp;mm/s for the first layers to 50&nbsp;mm/s for the infill.


I've also reverted back to the old PTFE tubing as I noticed that the Capricorn was giving too much resistance to the filament. Nope, still skipping.

I've noticed that the extruder gear grips quite firmly onto the filament, so much so that when it starts slipping it actually eats away the filament until it breaks. It's almost like there's a clog somewhere but the tubing is clear, the hot end is clear (I've cleared it and checked multiple times), and the nozzle is brand new.

What else can I try? Have I missed something? Apart from the changes listed above (carried out after the extruder started skipping), the printer is absolutely stock, firmware and everything.

UPDATE: I've changed the factory hot end bloc with a brand new one, changed PTFE tubing one again, making sure it's as close as possible to the nozzle (unscrew nozzle 1/2 turn, fit PTFE, screw nozzle in) but it didn't change anything at all. 

The extruder still skips steps as it can't push the filament out of the nozzle. Pushing it manually feels nice and smooth until it hits the nozzle, where I can feel too much resistance.

UPDATE 2: I've modifed the following parameters on the EEPROM to limit the filament flow:

M203 Z5.00 E25.00
M201 E1000


I've also crancked the temperature up to 220°C but it made no difference whatsoever. What I've noticed is that, after cleaning hot end and tubing, it starts skipping after 1 hour of printing, every single time without fail.

UPDATE 3: I've checked the input voltage from the PSU and it's 24V; the Vref for the extruder is 0.744V, so everything looks as expected.

UPDATE 4: The extruder idler pulley has a compression washer to hold it in place without impeding idle spinning; it is usually mounted in the order idler pulley, compression washer and bolt. I've noticed that the pulley wasn't spinning freely this way, so I inverted the order to compression washer, idler pulley and bolt. The bolt head is small enough not to stop the pulley from spinning.

I've also increased the pressure the spring arm excise on the idler pulley, so that the toothed pulley grips more firmly on the filament.

This way I've managed to improve things although not solve them. It's been printing for the last 3 and a half hour without skipping but it's not a solution, as the toothed gear is chewing too aggressively on the filament. In just one hour a good deposit of PLA shavings has formed on the extruder, and I had to blow it away, and this never happened before this all started.
Since you've said you can feel a problem at the nozzle pushing it through manually, and since you say it goes away for a while after cleaning, you probably have somewhere that molten filament is getting into that it's not supposed to, then solidifying and jamming. Check that the cooling fan for the heatsink on the coldend is working, and that the PTFE tube is properly installed all the way through the heat break and butted up against the nozzle with no gaps or irregularities, and that the pressure fitting is holding it firmly and not allowing it to back out. If you can't find anything wrong, it's possible that something is just defective/damaged inside the hotend assembly.