I'm trying eSUN PETG on M2 with E3D v6, .60mm nozzle.
Three consecutive failures within 0.25 mm Z height of each other. All at Z~3mm. I'm very happy with print quality up to that point. (Layer thickness set to 0.25mm)
Failure is air printing accompanied by "clunk-clunk" extruder motor sound ". Tear-down always finds plugged nozzle.
After first failure, reduced speed and increased nozzle temperature. Start at 220C, then 230C, then 240C. I expected to see some improvement in response to significant slow down and increased extrusion temperature.
In addition to any suggestions, I'd like to know if the extruder motor getting VERY hot is normal. (finger touch = QUICK!! pull-back ) .
No, the motor does not usually get that hot - the nozzle does of course... Might be because your extruder temp is too low - you should be melting the PETG at above 240°, (I'm not sure the exact number for the e3d nozzle), but it sounds like it might be having to struggle too much to force the filament in, and it is not melting fast enough to get out of the way.
It might also be jamming, and stripping the filament. (Sounds like it. The clunking sound.)
Measure the filament diameter, make sure you have the right settings (the diameter does swing, it ain't a "set it and forget it" proposition).
When it does the clunk-clunk thing - retract the filament completely and look at the end of the filament - has part of it been cut away in an arc? That's stripping, and it happens when the tension is too tight against the filament. It results in the filament flow stopping completely in your print. (Air printing.)
You might need to loosen that filament drive screw up just a bit - there should not be deep grooves from the gear teeth in the end that is feeding through the filament drive, just enough to catch and push it through.
Raise your temperature to the 240°+ range. (You might need to go higher than that, depending on your nozzle.)
Slow printing down to
under 60mm/sec. (Trying to force too much in too fast is another quick way to wreck your nozzle.)
And let us know how the next one goes.
I've been trying to print my fly fishing reel in the black PETG and I've really been putting off playing with the setting because I didn't want to read through 35+ pages of the other PETG thread to find out what works and what doesn't. 
