The elusive and to often "live with it" attitude that the early Z31 car owners have had to deal with may now be SOLVED. I'm referring to the cold start performance of the 1984 and 1985 300ZX when the car would stumble, buck and/or hesitate do to a "lean mixture" condition until the engine would warm up.
Recommendations over the YEARS from very knowledgeable people range from changing ECU's from other vehicle years to changing multiple sensors from the exhaust up to the CHTS. The FIX is simple, which is why it was probably overlooked all these years. The short version... WD40 in the EGR Valve -Solenoid. It WORKED on my 1985 300ZX -GLL.
For the entire story and the thought process behind this fix go to the original link (from the Connecticut Z Car Club {CTZCC.com}) and is attached:

CTZCC.COM ? View topic - Cold Engine/Transmission "Bucks" until warmed up

 

Good post trophy235. Thanks for doing all that legwork and reporting back

 

i wonder if the control strategy changed in the later years of the Z31, where it wanted to run EGR even in warmup? Regardless I'm glad you fixed your issue, nice to see ACTUAL troubleshooting and evidence other than just "replace x part(s)"

 

I'm just hoping that other Z31 owners try the WD40 before spending unnecessary $$ to fix the "lean" stumble. Simple fixes are Z way to go. Good luck to other stumblerZ.

 

I read the linked post and I'm not sure what happened at the "update" to "update to the update" point. It seems like a new EGR valve solenoid was installed with a new PCV and the problem came back. But, with the old PCV valve and new EGR valve solenoid, all was good?

So, the problem was ultimately... an aged EGR valve solenoid and dirty injectors?