1986 Toyota 4Runner Won't start

Car was turning over but wouldn't start up. Had the fuel pump and filter replaced, and a tune up- new coil wire and spark plugs. It has been towed three times this week, and everytime i brought it home from the shop they told me it was alright. I have dropped $500 in the last week. Can't really afford much more than that. Just called the shop and they said it might be a computer problem. If anyone has experienced this or has any advice let me know. I'm getting frustrated paying money, bringing it home and it being dead the next morning. I also can't afford to put much more money into it, but I also can't reallly afford a NEW car either....Any idea how much a new computer costs? I'm scared to find out. I'm also worried that i'll pay for that and then it won't start AGAIN. Anyway, any advice would be great. oh and i love in northern michigan (coast of lake superior)

so its really cold and snowy if that makes any difference.