Hello all! I'm new to this forum, but I'm sure I'll be posting several questions on here from now on

Question I have is -- I have a check engine light that won't seem to leave me alone. Have had it checked by O'Reilly's, Pep Boys, Autozone and they all tell me the same thing, that all 3 of my O2 sensors have failed. I've checked the wiring, and it all appears to be complete, without any tears, cuts, etc. Have used a multimeter to check the O2 sensors, and they all seem to be giving me "valid" readings. I'm at the point where I almost want to just replace all them to rule it out, but I can't fathom how all 3 would be bad at once. Is this indication of a possible bad catalytic converter? I did, in the past year, replace the spider injection with the new "updated" version. Before that, it was absolutely gushing gas into the engine. Could that have torn up the O2 sensors or cat?

Any suggestions? I hate like heck to just replace parts -- it's not a cheap endeavor just on a whim....

FYI -- the vehicle is a 1998 Chevy Blazer LT 2WD. Currently has 168k on it. Got it with 163k.

 

If the upstream and the downstreams are all sending codes dont suspect the sensors are bad make sure your catalatic converter isnt bad thatll trip all 3 also exhaust leaks more then likely around the manifold donut also running rich to long or prolong exhaust leaks by the manifold or bad catalatic converter can cause all 3 to go out i wouldnt just replace them tho without checking for leaks and having the converter checked first youll damage the new sensors just as fast with a leak or bad catalatic converter and there pricey lol

 

That's what I'm thinking because it wouldn't make sense that all 3 would just fail, just like that. Once I get some other stuff I'm working on, on that vehicle, I'm going to take it into an exhaust place and have them take a look. As far as I know, the exhaust system is original and I am pretty sure I do have some form of an exhaust leak, as I can hear something from underneath that indicates such. What does a stock exhaust system usually run -- ballpark figure?