Ultimaker 3 Extended prints pores in walls
While no expert, I'm wondering if you're going the wrong way with tweaking your parameters. 

If I'm reading your question correct, you have a fairly large nozzle (it's a 0.8&nbsp;mm?) and then you're using ABS which requires more heat (230&nbsp;°C nozzle temp) than say PLA does (typically 190&nbsp;°C). Along with that you are using a fairly thick print layer of 0.3&nbsp;mm, where I've normally only used a 0.1&nbsp;mm layer height. You add all this stuff up and it seems to me the nozzle temps are probably not keeping up with the amount of filament you are trying to extrude, and due to these things, you're seeing the gaps in the print. 

My thinking on this to fix your issue is to do a couple of things. You can slow down your print speed to allow the heating element to keep up. Secondly, use a smaller layer height. Both of these things should help, but will increase print times dramatically. You could also go to a smaller print orifice. Lowering the orifice size to 0.4&nbsp;mm would again, increase print time, but would mean less filament extrusion and the chance for the nozzle temps to keep up with extrusion needs.