Check engine light blinking

Oh good god I dont think it's ever had a "tune up". My bf went to look at it, when it sits and idles its fine but as soon as u put it into drive the idle drops to the point where it almost shuts off (ive never had a problem with this car in the summer but as soon as winter hits it acts up) last winter I put 3 alts. And 3 batteries into itr before it stopped leaving me stranded. Once again it's winter and it was fine up until last week.

I bet u that's what it is, first scan done on car said random miss fire. 2nd scan said cyl. 4 miss fire. I replaced all spark plugs and it's still doing it. Check eng light came on again now it says emissions. Car is goin through gas like crazy. Thank u so much if anymore ideas pls let me know?

It will do a little chuck (drop in rev, just enought to notice and make me look at the guages, I have a 15min drive to work and my heat guage is always low by time I get to work and car has barely warmed up) while driving then the check engine light comes on and blinks. If I come to a stop this is when it idles like it is about to shut off (but never does die) when I take off it once above 1 rpm it runs fine. Today was first day it had a little hesitation while driving it. Sometimes it's a lil rough shifting gears. Like it will rev higher then normal before shifting but it doesnt do it everyday or everytime I drive it?