I have a 1984 Datsun-Nissan 300ZX Turbo AT with 71,800 miles that will stall immediately on cold start unless I control the idle speed by keeping the accelerator pedal depressed. It will stall until I warm the engine up and after that it will idle poorly and eventually stall out again. Car will hesitate slightly at low speeds but acceleration and driveability on the highway is normal. If I am idle too long at a stop light, the car will stall. I have to keep it running by placing the shifter into neutral and giving it gas. Furthermore, if you allow the car to warm up, shut the engine off and try to start her again, it takes a couple of long cranks to get her fired up again. Spark plugs, wires, distributor, distributor cap and rotor were all replaced by Buckeye Nissan. The cylinder on the Idle Air Control Valve makes a clicking noise at regular intervals when the battery is connected but the car is not running. Also, if you place your hand over the cylinder on the IACV, you'll feel a thump. Does this mean the solenoid that actuates the valve in the IACV has failed? I performed the ECU diagnostic to obtain the ECU codes and they are:
22 Fuel Pump Circuit
23 Throttle Valve Switch VG30ET
24 Neutral/Park Switch
31 Air Conditioner
34 Detonation Sensor VG30ET
It doesn't look like anybody on this forum is jumping on this, so here's what I'd suggest. It certainly sounds like the IACV - or the electronics driving it - are where you should look. Note that the early 80's was the many vacuum hoses on each engine era - they did things that are all electronic now. My other suggestion is that you might want to look at some Nissan 300Z specific forums for clues on this. Apparently, there are quite a few.
https://www.google.com/search?client=firefox-b-1-d&q=300zx+Turbo+forum
Yeah, I figured I was the lone Datsun-Nissan guy in this forum as every else is has got a Ford, GM or Honda. Not many people know much about these cars, but you're right. The ECU typically goes out on them as they're almost 40 years old and vacuum leaks can cause similar symptoms. The Z forums were the first place I asked, the only reason I asked here was because I thought Scotty might know. I'm about 75% sure it's the IACV or IACV Auxiliary Air Control Valve as Nissan calls it. I'm going to remove it, clean it and see what happens. If I discover that's the problem, I'll probably have to delete it and get a block off plate for the upper intake plenum as they may be limited in availability or discontinued from Nissan. Thanks for taking the time to reply.
You're no longer the lone Datsun-Nissan guy on here! 🙂 I also have an '84 300ZX, an AE, with a very similar problem. Although, I definitely have vacuum leaks and my 1st priority will have to be getting the transmission rebuilt. Did you get this problem figured out?