Volvo: volvo 240DL, accelerator pedal, dianostics

Question
I have a 1986 (the title says 1985, but the body style is an '86?) 240DL wagon. I am having what i presume to be an electrical problem: the car will just die everytime I stop. When jumped off, it will run, but if I have to stop at a traffic light it will die again. Some times it stalls, and sometimes it just dies without warning. It used to run great. I haven't been able to drive it in about a year, so I was wondering about how much this problem could cost me to have it fixed. I love this car and want to fix it, but will it be financially worth it to have it fixed? (The shop I took it to told me they can't tell me anything about it without running dianostics, which will cost me almost $200 on top of whatever the cost of repair, which I just can't afford.)Anything you can tell me will be greatly appreciated. Thanks for your time!

Answer
good news: your problem is very minor , bad news : finding someone that won't rip you off.  well there are 2 areas of concern with problem, does this car have an EGR valve , i have an 87 and mine doesn't, if yours does, ( there will be pipes coming out of the exhaust manifold that go back into the intake manifold, controlled by an EGR valve) and if it's stuck in the open position this problem will occur, the more likely problem is with the idle bypass valve switch or bypass valve (2 1" black hoses coming out of it under the intake manifold) you might want to check the throttle switch (there should be a clicking sound at throttle when accelerator pedal is pressed, you can do it with your hand under the hood, there is a black plastic switch half inch wide and 2 x3 inches long this must click)
if it doesn't that needs to be replaced and IS the problem, the valve needs to be checked by a mechanic.