[Feighn and Handel][1] proved that they're all coherent in 'Mapping tori of free group automorphisms are coherent', *Ann. of Math. (2)* 149 (1999), no. 3, 1061--1077.

 [1]: http://www.ams.org/mathscinet/search/publdoc.html?arg3=&co4=AND&co5=AND&co6=AND&co7=AND&dr=all&pg4=AUCN&pg5=AUCN&pg6=PC&pg7=ALLF&pg8=ET&review_format=html&s4=feighn&s5=handel&s6=&s7=&s8=All&vfpref=html&yearRangeFirst=&yearRangeSecond=&yrop=eq&r=6&mx-pid=1709311