My engine (4.3 vortec cfi "W" code) Makes a horrible smell out of the tailpipe, and idles irradically. The check engine light comes on and goes off spurratically as well. I have already replaced the fuel injector unit, and my first guess is the EGR valve. Any thoughts?

 

i was gonna put up a new topic about that. i have the same problem and i need help too.

 

It was the oxygen sensor. All good now.

 

which one? i thought there were 2 or 3 o2 sensors i think i might have a similiar problem