what is this little black box with switch?

[SoLoDoC]

While replacing my side marker bulbs i noticed that in the back of the engine bay on the passenger side there is a small black box with a switch in the middle and wires running out of it from the bottom. Just what is this. I can take better pics of it if necessary. Also, like the idiot that I am, I fiddled with it last night and this morning when I went to start my 1990 S13, nothing happened. So I popped the hood and pressed the switch then was able to start the car. Now all afternoon my car has been acting funny. Difficulty starting with rough idling until i really rev it up. If anyone has insight in these two matters I would appreciate it. Thanks in advance.

[240 Trainee]

Well, thats not OEM, I am pretty sure. I would trace the wires and see where they go

[FliMSiCaL]

that is definitely not stock, and from your symptoms, it sounds like a kill switch. removing it doesn't look fun.

[Bruno240]

yeah it sounds like a kill switch, and maybe the wires are getting lose if you are getting a rough idle.

[cyrus240sx]

i had almost the same thing.... only its just a switch underneath the dash that was spliced between the ign circuit.......

[SoLoDoC]

I'm thinking now that the rough start and idle may be attributed to cheap gas at Walmart. I have never filled up there before but it was on the way home.

[heavy1metal]

maybe a speed governer killer? Which doesn't apply to the not firing up(shrugs). What happens if your car is running while you flip it?

[574-240sx]

could be left over from a previous alarm.

[ETTInnov04]

I was thinkin along the same lines