I have a 1998 tacoma 4wd 2.7 4 cyl. and it is cuting out and backfiring alot. I ran the codes and i came up with a o2 sensor. I replaced it with a new one and didnt change. I just cleared the codes tonight and now it will hardly idle. the cut out is mostly on the low end

 

I had a similar issue on a 96 dodge dakota (i Know not a toyota) and it turned out that after i replaced the o2 sensor the new one got fried almost instantly after i started the truck

 

You replaced "it"? There's more than one O2 sensor.

 

in any case, a bad o2 sensor won't make the thing run -that- bad. just rich

but it will get contaminated and fail from whatever else is causing the problem

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test MAF first....MAF issues typically show up at idle speeds first