Hey all. I've recently acquired a 280ZX, which has shown me the beautiful world of Z cars. Being a valet, I've always enjoyed driving them, but owning one is an entirely different story...

Anyway, it's an 83 280ZX, 5 speed, L28E non-turbo and a blast to drive. When cold starting it, it'll slow-crank before turning over. To be honest it may need a new battery, but I doubt it. Once started it idles fine. The problem is when I press the accelerator soon after cold start. It will flutter and almost die before actually revving up. The faster I press the pedal the more pronounced the flutter and there may even be detonation in the exhaust. However the problem goes away after a few minutes of idling or a minute or so of driving. Furthermore, this didn't happen during the string of 100+ days this summer and has only manifested recently with the drop in temperature.

I've had a similar problem with a 78 f100 in which I found out the butterfly valve was stuck closed and just cleaned it. But the 280Zx is EFI and I'm not sure where to begin. I checked the throttle positioning sensor and it seems to be working fine. I talked to the previous owner and he mentioned hitting the thermostat with this stuff called "stabilizer" that he said is available at VW dealerships.

I'm guessing the thermostat is stuck on a position that is only suitable for hot days?

 

Welcome to ZDriver and to owning a 280zx!

It's either (or both) the cold start valve or air regulator. The cold start valve injects fuel right behind the throttle body when ambient air is below a certain temp. It's main problem is getting clogged w/ carbon. The air regulator controls extra air intake depending on ambient air temp.

Download the FSM here: www.xenons130.com/reference and start diggin.

 

Actually there is what is calle a cold start injector that sprays extra fuel into
The intake on cold starts... It's located on the intake manifold right after the throttle body... Check to make sure the harness is pulsing on cold starts... U can buy what's called a mood light for checking injector harnesses at harbor freight. It's basically a light bulb attached to two metal pins that plung into you harness.. If the harness side is working go after the injector itself

 

^^^ I undeleted your post because it was a good post.

 

just to avoid confusion the thermostat being stuck would only do two things... Either make the car take a long time to warm up or overheat the car. It really has nothing to do with fuel and air on cold or hot starts... If your coolant temp sensor on the other hand read too much resistance or too little in relation to what the ecu expects to see at that point it will affect fuel/air ratio and cause issues... Just start with what Nismo said and check the cold start and just enjoy working on your car

 

Thanks nismo

 

Thanks a bunch guys, I'll update when I get it taken care of.

 

Update: I haven't gotten a chance to take a look at the air regulator and the cold start valve. Frankly, since I originally posted this the problem disappeared and it started right up for the past couple of weeks. But the last two times I turned the key, the battery had to cold crank it for about 3 to 5 seconds. Definitely the worst it's been so far. I plan on checking on the air regulator on friday. I took a look at how it works and I think it will be harder for me to accidentally break it.

 

Don't also rule out the possibility of the Cylinder Head Temperature Sensor(CHTS) those things can do some funky things and you can have a car that will run perfectly fine when warm, but sputter, pop, or run really weird when cold.

 

I have the same problem with my 1983 280ZX. The coldstart works, I've replaced the fuel pump and the mass air flow unit. The car won't start when the motor cools below 80 degrees. The throttle body sensor seems to be working and has new injectors.. If you determine what is wrong with yours, please let me know.