I've been told to clean my o2 sensor and replace the cat, because I keep failing emissions. The cat will be taken care of saturday, the shop agreed to change it free since I have the warranty. Now when should I clean the o2? (before or after changing the sensor). And what it the best thing to clean it with? Thanx

 

Is your car throwing a CEL for either the o2 sensor or the cat? The cat can be getting lazy but still be working and not throw a code, but the o2 sensor is another story. Sensors such as the o2 sensor are either working or they are not. It is not that complicated of a sensor.

 

nope, no cels. Someone just told me before I resmog I should clean the o2. . I'm just confused on how and with what to clean... Thanx

 

You cannot clean an O2 sensor. It is either bad and needs to be replaced or it doesn't.

 

Its not bad. It doesn't throw any cels... Why the hell did this one guy(can't remember his name) tell me to clean it? Doesn't that help at all with smog? weird

 

If you aren't throwing codes, the O2 sensor is obviously working correctly. Your problem exists elsewhere.

Have you replaced that ECU yet? Have you checked the base ignition timing?

 

Yep, ecu replace with stock p72 and it stopped running rich. Timing is a 16* btdc. I'm replacing the cat tomorrow. Could the running rich have messed up the cat?

 

Running rich too long can mess the cat up. So it depends. It makes the brick work double time to burn off all the hydrocarbons, which in turn don't all get burned, which in turns makes the cat lazy.

 

Anyone hear of this fuel additive called "guaranteed to pass smog" at autozone? Supposedly my friend used it in his dsm and it passed smog, even tho he was running on only 3 clylinders... weird

 

running too rich could possibly hose the O2 sensor. You can test o2 sensors

http://clarks-garage.com/shop-manual/fuel-18.htm

(most all o2 sensors are exactly the same and work in the same manner)

ps, anything you try to "clean" the o2 sensor with, will probably just ruin it.