Hi classic-z-car-community,
I have some trouble with my 280z engine - it is starting very hard - needs a lot attempts and then runs very weak - after getting warm the engine run is getting better, but takes gas very bad - nearly stopping when cold - and misfiring often ...

With the following link you could experience the behavior:
https://youtu.be/79MqGnp45u4
... the engine run half a hour before, so was not too cold. without this it would need 8-10 start attempts until coming to live ...

What did I try hitherto:
1. as the fuel pump that was mounted (also not original) whas very loud - I ordered an aftermarket pump from zcardepot.com (https://zcardepot.com/electric-fuel-...80z-280zx.html) and mounted this ... it also is getting very loud when the engine is running 
2. i checked the spark plugs - exchanged them to the originally recommended NGKs - and adjusted the distance to 1,1mm als recommended in the service manual
3. checked ignation cables and connectors - all looks normal
4. checked ignation distributor - is new and looks normal - adjusted the ignition moment towards preignation - so the engine runs a bit smoother
5. removed the from the previous owner in Phoenix mounted open sports air filter and mounted the repainted original filter box with a new K&N filter

The previous owner of the car removed the EGR and replaced the air regulator with a manual valve, what should have worked well for his context in Phoenix.

Would should I do next to optimize the engine run?

Does anybody have the some experience and a solution for me?

I am very thankful for every hint and help!

thank you, Chris from Austria

Sounds like it's running very lean.  You probably have a leak in to the crankcase from one of the PCV hoses.  Examine all of them, including the one in to the block under the intake manifold.

Make sure all of the hoses in this picture actually go somewhere important.  All of the air that goes in to the intake manifold needs to go through the AFM.  So check the hoses from the AFM to the manifold also.

If you can, confirm that your fuel pressure is correct also.  Pumps get noisy when they have to push hard through something like a kinked line or blocked filter, or when they have to pull the fuel against a restriction.  You could have fuel starvation.

Edited September 26, 20177 yr by Zed Head

Another thing that happened to my '77 was the EGR tube came loose where it connects to the intake manifold. It rotted a golf ball size hole in the soft aluminum. Get a handheld mirror and look under the EGR connections. It was a huge vacuum leak that I chased for a month after buying the car.

Nissan had a recall for it to. If it was dealer fixed there will be a sticker on the underside of the hood, passenger's side by the hood vent. Mine had the dealer fix, a circle clip on the connection, but somehow rotted out anyway.

21 hours ago, Zed Head said:

Sounds like it's running very lean.  You probably have a leak in to the crankcase from one of the PCV hoses.  Examine all of them, including the one in to the block under the intake manifold.

Make sure all of the hoses in this picture actually go somewhere important.  All of the air that goes in to the intake manifold needs to go through the AFM.  So check the hoses from the AFM to the manifold also.

If you can, confirm that your fuel pressure is correct also.  Pumps get noisy when they have to push hard through something like a kinked line or blocked filter, or when they have to pull the fuel against a restriction.  You could have fuel starvation.

I will check this on the weekend and get back with results - thank you very much for your indications!