rough idle?????

**01ls1ws6** · 09-25-2007, 04:01 AM

I have had this problem for a while now, with no luck fixing it. My car idles rough and has got consistantly worse over the last 3 months. ITs been to the dealer multple times and they say its running fine, i haven't really lost any performance but now ses light is on!!! I think it was po430 catalytic converter failure, but the guy at auto zone thinks it an o2 sensor. What do you guys think, and also has anybody taken their car to get the cats replaced. because i got a letter in the mail stating that our cars have premature cat failure and they will replace them for free. Any and all feed back will help thanks.

**jag42420** · 09-25-2007, 05:27 AM

I got the cat letter too (http://www.ls1.com/forums/showthread.php?t=35957). Since the dealership will replace for free, I'd take it to them. They'll let you know if it's a cat or the rear o2 sensor.

If you don't want to go to the dealer, you could switch your rear o2s out and see if the problem goes to the other side. If it does, it's the sensor. If not it's the cat. The cats on these cars seem to fail at random anywhere from 15k to 100k miles. I doubt it's a sensor.

**01ls1ws6** · 09-25-2007, 06:40 AM

thats a good idea thanks

**01ls1ws6** · 09-25-2007, 08:53 AM

will a bad o2 sensor cause a vehicle to run bad?

**jag42420** · 09-25-2007, 12:20 PM

A bad front o2 will, a bad rear o2 should not. A bad rear may cause mileage issues, but should not make it idle rough. Front o2 controls fuel mix. A bad cat would, which is most likely what you have. Signs of a bad cat are unnatural rattles in the exhaust when revved, the exhaust smells abnormal, there is reduced power (revs slower), or the car runs warmer than usual. You could have any one or combination of those, or even none that are noticeable yet if it's just starting to fail.