Engine Mechanical problem
1986 Volvo 240 4 cyl Two Wheel Drive Automatic 150000 miles

I just acquired a 240DL Volvo Wagon, and have a missing part that is suspected of causing the engine not to stay running.
The engine starts up, but it does not stay started, like it fades out. Before it stalls, I can press the gas pedal, and it has a delay response to keep the engine running for a second, and then it fades again until it gets gas - I cannot get it to idle at a constant speed.

When I look in the engine compartment, I can see that it is missing something - I do not have a manual to know that missing part is - hopefully someone can help me identify the part, and perhaps that is what is needed to repair the problem.

I have circled the cut wires, and the plug in to the item.

Thanks for your help.