CEL Problem Persists Depsite Repairs

[stateofidleness]

Had the same exact codes. 2 cleanings of the MAF made it stop for a little while and then I finally got tired of it and replaced it. Voila. No more CEL.

[Jager]

Have you replaced your gas cap lately?

[thom4782]

Now that you ask, I did replace the gas cap. Could the new cap have something to do with the CEL continually returning?

[Jager]

Is it OEM?

It needs to be factory original otherwise you could have problems.

[Wayne 962]

Hmm, these are tough to narrow down. I would perhaps think about doing a smoke test to find possible vacuum leaks. At least that will eliminate them as a potential problem? I've got an article on this procedure here:
http://www.pelicanparts.com/techarticles/Boxster_Tech/21-FUEL-Vacuum_Leaks/21-FUEL-Vacuum_Leaks.htm

-Wayne

[Jager]

Originally Posted by Wayne at Pelican Parts

Hmm, these are tough to narrow down. I would perhaps think about doing a smoke test to find possible vacuum leaks. At least that will eliminate them as a potential problem? I've got an article on this procedure here:
http://www.pelicanparts.com/techarticles/Boxster_Tech/21-FUEL-Vacuum_Leaks/21-FUEL-Vacuum_Leaks.htm

-Wayne

Wayne! Dude! Where have you been? You have been a member since 2007 and I am now just seeing a post from you on this site? You need to visit more often; there is a great group of Boxster enthusiasts on this site. BTW your book 101 Projects for Your Porsche Boxster has been very helpful.

Hope to see you post more often.

[thom4782]

Thanks everyone for the advice so far.

After the last round in the shop, the CEL popped back on the first start after 50 miles. All the secondary air parts have been replaced now. So I am beginning to think its one of the O2 sensors. Two questions. First, with a 91K car, can an oxygen sensor be bad without throwing any of the codes. In all time, no O2 code has ever been seen although the mechanic once mentioned a sensor was slow to react. Not sure how he knew this. If yes, is there any way to tell which sensor may be bad? Second, is it true that after resetting the codes, the car's computer waits for 50 miles until it checks again for CEL related codes. Thanks