pre cat code

[Tileman]

Hi, I just bought a 1998 Mazda Protege For my 16 year old daughter. The car was well taken care of by a college student. It has 150,000 and we got it for a great price. The reason for the great price was the check engine light is on. The code is for the pre cat, or warm up cat. Upon further inspection I found a cracked Exhaust manifold. I replaced the manifold, cleared the code,drove it for a few days and the light came back on. OK so here is the question. Could the o2 sensor(s) be bad and causing the code? She seem to run good but has a slight surging idle, and i noticed a lot of pining some times, not all the time. I am sorry for the long post, but I don't want to start throwing a bunch of parts at this car if I don't need to,ie.. pre cat. Thanks for your help (uhm)

[mannydingo]

Since oxygen sensors are a maintenance item anyway, you should buy one even if it doesn't correct that particular problem. If it has never been changed, it might solve the problem. I'm familiar with the location of that sensor. I recommend you buy an O2 sensor socket. I buy cheap tools often but I recommend you buy one of those from Snap-On or any other "real" name brand as the others tend to slip a lot. You will need to align that socket very square onto the sensor or you will start rounding out the old one and can get to a point where you can't take it off. I used a cheap one to get the sensor off at the junkyard and ruined 4 of them in my attempt. I finally got a 5th one off but had to wait a month before another 2nd gen Protege was at the yards. The other yards had high mileage cars. Getting any other tool to get it off after the nut is rounded is next to impossible unless the whole assembly is removed for that location.

[Tileman]

Since oxygen sensors are a maintenance item anyway, you should buy one even if it doesn't correct that particular problem. If it has never been changed, it might solve the problem. I'm familiar with the location of that sensor. I recommend you buy an O2 sensor socket. I buy cheap tools often but I recommend you buy one of those from Snap-On or any other "real" name brand as the others tend to slip a lot. You will need to align that socket very square onto the sensor or you will start rounding out the old one and can get to a point where you can't take it off. I used a cheap one to get the sensor off at the junkyard and ruined 4 of them in my attempt. I finally got a 5th one off but had to wait a month before another 2nd gen Protege was at the yards. The other yards had high mileage cars. Getting any other tool to get it off after the nut is rounded is next to impossible unless the whole assembly is removed for that location. Thanks, I've already had both sensors out so thats not a problem. Is there a way to test and see which sensor is bad off the car?