hey my 99 blazer has had the cat. conv. chopped off and replaced with a straight pipe. it now stumbles and falls on its face when you go from a dead stop. and if you hit the passing gear it revs high but goes nowhere. I can also smell a little bit of raw fuel. I know im probably the only one on here that doesnt know for sure, but does it have to have one due to the o2 sensors???

 

yes it does bc there is no more cat your o2 sensors have to be by passed theres a kit online you can get to do this so google it and by passing the o2 sensors will give your truck alittle more power not much but its something

 

Is the Service Engine light on, by any chance? What do you think it's there for.. to annoy you?

Yes and no. doesnt affect the primary O2 system in any way. Only the after cat O2's whose job it is to monitor cat efficiency. Since the cat is obviously 100% inefficient, I suspect the PCM just MIGHT put the engine in 'limp-in'. Wont know until provost has the codes read out.
I'd launch into a tirade about people who still think a cat affects performance.. but what the hell. I've been doing that twenty years and its getting old..
Plus it was GM bead type cats in the first place that did have problems...

 

Well, it will definitely affect performance if the internals burn out and break up, plugging it up.

 

Umm yeah.. been there, had that. Except that gets me into yet another rant about people who buy from no-name mom & pop stations. Like my kid did when he borrowed my Probe.

1 tank from peppy and no rattle to a hockey puck in the poop chute.