I have a 1984 pickup, California emissions, and recently bought a replacement carb on Amazon. When I received it I found it had an extra diaphragm valve on the choke, which my old carb didn't have. what is this? I can't find any info on it in the FSM or online searches. Do I need to purchase a California specific carb, remove this part, or hook it up to some vacuum source? Any help is greatly appreciated, Thanks.



"extra part"

 

There is a space in the profile to indicate your town and state - that info is often useful.
For instance
Just because your truck is (or was) a Cali truck doesn't mean it is in Cali now.

 

That part is the Air Conditioning (A/C) Idle-Up diaphragm. If your truck has air conditioning, a vacuum hose connects this diaphragm to the Air Conditioning Idle-up Vacuum Switching Valve (VSV).

When you turn the Air Conditioning system on, the Vacuum Switching Valve pulls a vacuum on the diaphragm, which moves the throttle linkage, which raises the idle a little bit to compensate for the load the A/C compressor on the engine.

If your truck does not have air conditioning, you can just leave it alone, or remove it if you like. It does not do anything if the A/C system is off or not installed.

 

My following comments is based on my 1987 truck with California emissions:

If your 1984 California emissions carburetor is like my 1987 California emissions carburetor, then the picture you posted is not a true California-spec carburetor. I suspect that there were some differences, but I'm not seeing the ports for the EBCV (Electronic Bleed Control Valve). Since the California-spec carburetors were a feedback carburetor, it used an O2 sensor to regulate additional air into the carburetor to adjust the air/fuel mixture. The additional air is feed by the EBCV.

In the following picture you can see one port for the EBCV at the top, above the red, and white-sleeved wires, to the right of the choke.





In your picture, they would have been above the black wire that bends 180 degrees, that goes to the OVCV (Outer Vent Control Valve), and right next to the shinny screw.

Doing a quick search for NTK O2 sensors, it looks like the same O2 sensor covers 1984-1988 trucks, so it looks like your '84 is similar my '87.

 

^^ That is some good information I was not aware of Slow-mo. I have never seen a California spec. carburetor in person.

If someone knows the difference, if any, between 1984 and 1987 California spec. carburetors, feel free to share your knowledge!

 

Thanks for the info guys, perfect.
@slow-mo, my carb actually does have the EBCV port, i just grabbed that pic off the internet, glad it wasn't the one I ordered.