The engine in my 97 4dr has developed a rattle recently that I can't place. Reading around and personal exploring led me to discover that the tensioner was shot and I replaced it with no effect on the sound. I am given error codes saying my emissions sensors are tripped. Does anybody have any ideas?

 

update: going to try out a new alternator and see how that goes, also, while it only happens at lower rpm's and at idle, when warmed up it can't be heard at idle but rattles when I rev.... anybody dealt with this before?

 

It is helpful to the forum to give info such as the DTC numbers. It is also helpful to tell the forum the history of the Blazer and engine: no. of miles, is it burning oil, what are the recent mechanical repairs or mod's. One trick to determine if an alternator's bearing are bad is to use a 1" PVC pipe or short broom stick to touch on the alt to 'hear' what's going on.

 

Yeah I hear you, I'm fairly new to the site. A little more tinkering has shown it's not the alternator at all, appears to be an issue with the catalytic converter. Question is, how necessary is that exactly?

 

Necessary for inspection, could be as simple as loose shield on the cat which you can remove or loose internal stuff which will mean a new cat

 

thanks, it has 190k on it and will be due for an oil change soon, I tapped the a cat a few times and didn't hear anything rattling around, should I be looking somewhere else or keep at the cat?

 

Did you check to see if any cat. heat shields are rattling by touching the frame or body work? It may help to put it on a lift and run it while someone gets under the SUV to see what's moving around and touching the frame. Caution: Have heavy gloves on so you can touch the exhaust pipe while hot.
In your post you said: 'I am given error codes saying my emissions sensors are tripped. '
What are the error codes that were shown? That may give a clue to what's going on.
One possible trick to try is to go to a Salvage Yard and get an exhaust system matching yours. Then you could try swapping it out and even cut off the cat. and see if the rattle goes away. Do your research before hand because every body style has a diff. exhaust system. Ex. A 2 door exhaust won't fit on a 4 door and so on.