Anyone know what this is?

I can't really figure out it's function. The "plunger" only moves back as far as idle speed....

 

Idle-speed kick-up device? If the linkage on the left side of the picture is the throttle linkage (sure looks like it) it's probably something to do with that. It's possible that it is a dashpot to slow down the rate of throttle closing, for either emissions or driveability reasons (or both).

 

Do you have A/C

 

looks like the HAC (High altitude compensator) on my old diesel land cruiser. It adjusted fuel mixture based on altitude...

 

gofaster is right...it slows down the throttle when you go to idle

wyatt

 

Thanks, you guys rock! Only 40 minutes from the time I posted

 

It's called a dashpot. It's an emissions control device that slows the throttle's return to idle after you lift off the gas to prevent a big burst of hydrocarbons (unburned fuel) that would result from the sudden throttling of the intake tract.

 

but does it work?
we had two that came that didn't work one was the vacuum line the other ,was the pot

 

I don't see how mine could work, when I push the plunger thingy all the way in, it doesn't even touch the throttle linkage.....?

 

That almost appears to be what increases the idle when the a/c kicks on.