Hey ! My car has been rough idling. the rpm goes up and down even when I am in park. I noticed something off and decided to snap a photo of it. Is there supposed to be some type of cap on this ? or possible some type of hose ?

What is this exactly ?

 

Looks like it's just supposed to be capped off:



For the rough idling, I would disconnect and clean the MAF

 

What is the MAF ? Sorry I am not really knowledgeable about vehicles.

 

Mass Air Flow Sensor, it's in between the air filter box and the throttle body.

 

Pick up a can MAF sensor cleaner, and spray the needle and be extra careful, they are about the width of a hair from your head and very fragile, once sprayed let air dry and then re install, takes a total of about ten minutes from start to finish

 

I'd start with solving that vac leak before going crazy. I agree, that is just a cap (as some of the other cars that engine is in may make use of that vac connection, but your Monte does not).

Solve that and see if that stops the rough idle.

If you still have a rough idle, considering your plug wires are the numbered AC Delco wires, I am assuming you have the factory original plugs and wires and I am also assuming you are well over 100K miles. I'd change plugs and wires next.

You may also want to review this for other maintenance that may need done:
https://montecarloforum.com/forum/fw...0-miles-46078/