Actually, the emissions solenoid was there to open the throttle blades slightly when the engine was running. There was a problem with the engines Dieseling after the ignition was shut off. And, closing the throttle blades far enough to eliminate this Dieseling shut off the air needed for idling. So the solenoid when energized opened the throttle to the idle setting.

But that's not all.

The engine produces a great amount of unburned stuff when you quickly take your foot off the gas. The high vacuum sucks too much fuel into the engine causing a momentary rich spike. So, many manual transmission cars got a solenoid to slow down the throttle closing. This could be bothersome as you'd take your foot off the gas and the engine revs wouldn't respond quickly.

Then there were the solenoids that kicked up the idle to run the air conditioning compressor without killing the engine at idle.

I don't know which use the solenoid would have had on your car, but unless you need it for emissions purposes I believe it can be left off.

R.