Burnt taste almost always means dry coil. Many reasons this might be happening.
1. The carto was not really full. I always use a drip tip on my cartos so I can drip topoff or look at the filler easily. After the condom method, let sit a bit, blow out excess, and vape a few hits, I almost always find I need to add more drops to fill the carto.
juice sometimes will need some heat to full distribute.
2. The
juice is too thick, and depleting near the coil faster than the
juice can wick. I would take a 3 mL bottle, add mostly the juice and then a drop or two of distilled water. So that you are adding maybe 5% water by volume. Might take more, but you don't want it too thin either, so experimentation is needed. A drop of PGA might do the trick too. Cartos like thinner juice.
3. If 1 and 2 don't do it, look at the coil. If it is sticking up a lot over the top of the filler (it is looped up and over the center tube in the middle of the filler), try pushing it back into the filler
carefully. Its easy to bend it over too much and crimp the center hole.
4. Your previous burnt taste actually burned the filler. That taste will not leave now, even if the carto is full. It
shouldn't happen at your power level, but it might have.
5. If none of 1-3 work, and it was a new carto, and others are doing this too, contact the vendor. 3.0 ohm should have no issues on 4.7V (Its about 7 Watts of power). You might try lowering the voltage, of course, but you implied a bit higher is good for you. It could be a "bad" lot, whatever that means, since I don't know what causes this if the carto is full...maybe there is a small part of the coil that is in a position that never gets near juice. The vendor might replace them, but most cartos are without return policies...OTOH most vendors want to know if they are selling faulty equipment, so YMMV.
If the clearo is CE2 coil technology, no they do not like high voltage. Even my 3.2 ohm clearo is plenty on 3.7V. If this DC is of filler-based technology...essentially like a regular carto with filler roll, you are likely having the same issue as above. Pushing voltage on cartos of any kind is kind of touchy. Wicking issues and singeing filler are relatively common. Thinning the juice or making sure the carto is actually full are the first steps.
