Yesterday i noticed that my 98 blazer (4.3l V6) has a serious power loss and also is shifting at high rpms (4,000). Not sure if its is causing the problem but recently my catalytic converter has begun to rattle from broken internal parts(smashed it on rocks...). If those broken parts blocked off the exhaust flow would that cause this? Im also hearing a loud hissing noise at higher rpms. almost like its the exhaust going threw a clogged up cat. Any help would be great. I am going to take the cat off and look at it. maybe gut it for now til i can afford a new one...

 

I am having the same problems with my 99 ZR2. I have replaced my TPS sensor, MAF sensor, all O2 sensors, and I still got the problem. I am in the process of getting the cat now. But I'm not sure if it will work. If you solved yours might you share what was wrong. I had a buddy that works at GM run the GM scan tool and he couldn't see anything wrong either. So again if you solved yours it would be good to know what was wrong. Thanks :-)

 

just pulla oxygen sensor before the cat and drive it to see if it makes a difference. If it fixes it replace the cat.

 

I pulled the o2 sensor like you said and still the same thing. So I looked at the distb. and still nothing so I took an EGR valve off of my 97 4.3 which I don't use that much and what do you know it works fine now. But I will update you within a week to let everyone know if it worked. odd that it didn't throw a code ... hummm

 

normally when the cat is busted up and blocking the exhaust pipe, you wont be able to rev it that high. plus the back pressure would be so high that you probably wouldnt be able to drive it. i would take it to a muffler shop and have them do a back pressure test. it only takes them a few minutes and then you will know for sure. but, i would say that your transmission might be slipping. when was the last time that you serviced it?

oh and chevy guy, a clogged cat wont throw a code, and neither will a slipping trans. those are both kind of "seat of the pants" things i guess.

 

sounds like the egr was the fix. Look at your old one,i bet its really dirty. clean it up and it'll work fine. they can die,but usually gets dirty. A open egr will cause a vacuum leak,lack of power etc.