Cold engine leans out till it stalls

[Th0m4s]

It's just a minor problem because this only happens the first 1-2 minutes after I start the engine but I'd like to hear your opinions to this.
When I start the engine cold I press the gas pedal down once for the fast idle to engage and a first squirt of fuel. Then I turn the keys and it fires up immediately and runs at about 2500rpm in fast idle. Then, after about 30 seconds or so it starts leaning out till it dies. I know it leans out because I installed a wideband AFR gauge. It goes up to AFR 16 and then dies if I don't play with the gas pedal a bit. So the question is: What could cause that lean condition?
The car has the factory 12A engine equipped with a BAE turbo drawing through a freshly rebuilt Carter AFB and 2-3 minutes after a cold start there won't be any problems anymore.

[TOOL]

No choke after the fast idle by the sounds of it.

Needs a choke system or turn the idle up. What's the idle speed set at (rpm)?

[Th0m4s]

It's set at 2500rpm. The choke is controlling it at a carter afb. It works like this:
The AFB has an electrical choke which closes a flap sitting on top of the primary throttle to limit the airflow. At the same time the choke linkage opens the throttle below that flap a bit.

[TOOL]

Oh right, yeah, you said that above.

That's way too high. My big BP idles at 1700rpm.

Sounds like the choke isn't working properly and the high rpm is trying to compensate for it.

Does it idle correctly once warmed up? Does it idle at 1200 when warmed up? If it doesn't, I would say you're only able to run on the main circuit and the idle circuit isn't working.

Is it ported?

[Th0m4s]

The engine is not ported and runs at 900rpm as soon as it's warmed up. I can set up the choke and fast idle like I want to. Everything is adjustable. Should I try to open the choke flap a bit maybe? Might be closed too much so the engine can't pull enough air through the venturis.

I'm still new to the whole carb thing and really don't know much about the choke so if I'm thinking in the wrong way please tell me.

[TOOL]

You want to close the choke more. Too much air, not enough fuel. That's why it leans out.

[Th0m4s]

The problem is the choke flap is completely closed. The only way to close it even more would be to weld it shut.

[TOOL]

Check your idle circuit then. Something not right there.

Pics help.

[Th0m4s]

It might be that I found my problem. I found an old manual about AFBs today and my problem is listed in it. It looks like he choke flap really is closed too tight. The manual says as soon as the engine is started the choke flap will be pulled open a bit through the engine vacuum (there's a vacuum line running to the electrical choke actuator). Mine doesn't do that. The manual states if that doesn't work the engine will start up but die a few seconds later because of too much fuel. In my case the AFR gauge shows a lean condition but I remember having a similar missleading reading in my first RX7 FC when the idle was set too low. Maybe I'm lucky and just adjusting the choke flap will solve my problem. I'll try that tomorrow. I'm also going to take some pictures and I'll adjust the fast idle down a bit to rund about 1500rpm.

[TOOL]

Fast idle at 2500rpm is fine. Once warmed up it should sit about 1000rpm. 800rpm is too low imo.

Good luck.