I took off the cat. and the check engine light came on and it ran, but not as it's usual self. dose it have to have the cat on it or is there anyway to bypass it & make it run right agin?

Thanks!
yamaha

 

by the way it is A "99" 4x4 blazer

 

yamaha f im not mistaken autozone or any parts store usually sells what are called dummy o2 sensors because the sensors do need to be hooked up or it will run like crap the dummy ones dont really hook up to nothing but will fool the computer. My friend had the same problem. Let me know if this helps

 

The down stream sensor has nothing to do with fuel delivery. That is most likely the reason for your check engine light however.

The running "not as its usual self" is probably because of the lack of back pressure that you now have in the exhaust system due to the absence of the cat. If you don't have the rest of the engine setup for the higher flow of the exhaust, you are going to have performance issues. And by setup, at the very least, a different cam to move the power band up in the rpm would make it much better.

May I ask why you removed your catalytic convertor? Aftermarket cats aren't really all that expensive... Plus there is a federal law mandating that all emissions equipment be on a vehicle. You could be charged a fine if you were to be found with out your cat.

 

Taking the cat off is a pretty big fine too. If youre trying to make your exhaust less restrictive, get a freer flowing muffler, dont take the cat off. The stock muffler is absolutely huge. If you really really want no restriction, put a section pipe in place of the muffler, but leave the cat.