my 94 jgcl 5.2 started acting up at redlights. meaning the truck is running alittle rough at a complete stop but runs perfect otherwise. i notice my volt gauge drop down dramatically to around the top of the yellow line when it runs rough. i can put it in neutral and give it alittle gas a gauge goes up to normal. just had a tune up and the alternator is new too. would it be the cranckshaft position sensor? if so where would it bein my truck? thanks for any and all info.