[2000SoCalBoxsterS]

Originally Posted by heyjae

The O2 sensors are just reporting the symptoms of the problem. Since they are the last sensor, there is so much upstream that could result in a O2 code. Cleaning the MAF may work, but if it doesn't, look for vacuum leaks. A vacuum leak could cause a rich condition. In addition to checking the usual tubing around the motor, check the oil cap, oil filler tube and oil dip stick. If that doesn't work, get a new MAF. Keep in mind there are 2 versions. It could be the air/oil separator, too. It's doubtful both O2 sensors went bad at the same time, but stranger things have happened--I recently replaced my O2 sensors and one replacement was bad from day 1 and it took forever to figure that out. Or take it to a shop and have them diagnose. These kinds of problems can take a ton of time to figure out without the proper diagnostic tools.

Thanks Heyjae, all good advice but please don't make me open up that mid-engine compartment again to look for the vacuum leak. I had read somewhere that if one O2 sensor goes bad it's best to change them all at the same time. I think the reasoning was that whatever fouled the first one probably messed up the others too or the new one will be more sensitive than the older ones and this could cause more CEL problems. My car is 8 years old but I only have 39,000 and change miles on it. Do you think some of the rubber could still have deteriorated just from age? I know the answer to that is probably, but I don't want to hear that. Weather sucks here today so I haven't test driven the car yet to see if my cleaned MAF and new air filter worked.