On Tue, 27 Jun 2017 13:37:20 -0400, "Mr. Luddite"
wrote:

I think Greg's explanation makes sense. We live in a world of
procedures based rather than old fashioned troubleshooting.
It's probably cheaper for Nissan to replace an engine than to hire more
techs or engineers to really dive into what the problem may be.


It is certainly false economy in this particular case but bean
counters look at the whole operation. Some guy predicted the cost of
running a real maintenance shop as opposed to simply running a MAP
shop and they do not allow any wiggle room.
At a certain point some old guy is going to say, "why don't we just
try a valve" then they may come to you and say it is fixed ...
probably giving you some ambiguous solution that does not involve the
valve.
It is like calling the Telco on a data call. They always say they did
not find anything on their end but the problem goes away.