Nissan Repair: idles rough then dies, snake oils, catalytic converters

Question
1992 nissan pfinder,just finished new trans set for 2yrs new ypipe,after stating for 1st time in 2yrs,it ran and idled perfect, after running a couple days, it would sart but not fast idle,would idle smooth then would start chugging or missing and idlle would drop lower and lower til it died,now it starts fine but goes into this phase automaticly,is it the idle sensor,oxygen sesor or both or something else thanks

Answer
Bad gas. Drain your tank and start over or fill it will premium and live with it until you can run it all through. If you don't drain it, it may take about 5 tank fulls to get the bad gas out. There might be some type of additive to help, though I am a firmly against the "snake oils" they sell as they are usually a waste of money and cause more harm than good. Careful with carb and fuel injection cleaners as they will clog your catalytic converters.

If there is a check engine light on, it would be helpful to know what codes are stored in the truck's computer. If you feel that it isn't bad fuel then it could possibly be a bad sensor. The code would tell us which sensor.