Nissan 300ZX efi fault

[Bob R. McElroy]

I had a similar problem with a 1979 280ZX.  The local Nissan dealer =
couldn't find the problem, but suspected the computer was failing.  I =
was in college at the time so I went to a salvage yard and purchased a =
used computer out of a wrecked 280ZX (NOT RECOMMENDED.)  I got lucky and =
it solved my problem, but when I look back at it, I shudder when I =
realize the problems I could have had.

Later, I wrecked the '79 and purchased an '81 280ZX (this one had T-tops =
and 145 hp instead of the '79's 130 hp.)  That car gave me no problems =
with surging like the '79 did.  Interestingly, the '81 succumbed to body =
cancer while the '79's body isn't terribly rusted (I still have the '79 =
and I plan on doing something with it, but what I'm not sure.)

You state that the '86 300ZX has two (2) computers?  Both of them can't =
be used for fuel injection control, can they?  As I recall, mid-'80's =
300ZX's could be optioned with digital instrument display panels or an =
electronically (computer?) controlled selective shock damping system.  =
Is one of the computers for either of these options?

I like the looks of the Nissan Z-cars and applaud your associates =
purchase of the 300ZX turbo.  My advice would be to try and unload the =
current Z on some sucker :) and purchase a used Z car from a Nissan =
dealer.  As I understand it, Nissan is currently offering reconditioned, =
used Z-cars for sale at selected dealers.  These used Z-cars even come =
with a warranty.  I'm not sure of the availability of this offering from =
Nissan, but it may be something of interest.

I hate to suggest dumping the car instead of fixing it.  No Z-car =
deserves that fate.  Maybe someone else has a better solution.

Bob McElroy

PS  -  I had a thought before I press the send button.  Could a plugged =
or damaged turbo cause surging?  That is, could it be fouled so that it =
sometimes produces a surge of air pressure that the engine isn't =
expecting?  Or the turbo shaft bearings so gummed up that the turbo =
stops spinning at low exhaust flow and stops up the exhaust system?  I =
guess one way to test the turbo is to watch the boost gauge (I think =
Turbo-Z's all came with boost gauges.)  If the boost suddenly falls off =
or spikes up, that would be a sign to investigate the turbo further.

BTW, in my dealings with Nissan dealerships (all in small towns in =
Midwestern America, specifically South Dakota) I have found them to be =
very knowledgeable and helpful.  That is very dependent upon the dealer =
though.
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The car is a Nissan 300ZX model listed below. Anyway long story short,
he bought second hand from a local car dealer after lots of warning
from myself. Has spent lots of $$'s fixing the usual faults with cars,
(hoses, leaking fuel seals etc ...) but there is one fault that even
the local Nissan (real 100% factory appointed) cannot resolve. I have

About 80% of the time the engine has a problem of surging then dying =
when
at 1700-1900 RPM it refuses to cruise at this RPM level. The engine =
still
accelerates and decelerates smoothly but will not run evenly whilst =
trying
to keep at a constant speed.