EDIT: Seems fixed after replacing the rubber PCV grommet for $3.

A while back I had codes, 15/33/34. At the time, replacing the coolant temp sensor fixed the 15 and the rest of the codes went away for a while. So it sat a few months and I started driving it again and once again code 34 comes back. I've tried 3 MAF sensors and all immediately trip the engine light within seconds of starting. It runs well and idles fine. Should I keep dropping MAF sensors in it or is there something else I can do to diagnose what's really wrong?

 

I let it sit for a day with the battery unplugged. Went through and removed and inpsect the air filter, MAF and ducting to the intake for cracks, found none. The PCV and other vacuum lines and fittings looked fine with no cracks or any sign of issues. Put it back totgether started up and no codes!

Drove it around for 10-15 minutes, no codes. Get home, turn it off, and let it sit while I worked on some cosmetic stuff. Started it up to put it away in the garage and code 34 immediately shows up.

 

After much poking, prodding, jiggling, and looking for vacuum leaks, I found that the grommet for the PCV valve seemed a little loose. Spent $3 and replaced the grommet and haven't had a code since. I am slightly beside myself over how much effort it took to figure that out.

 

Hi Sean. I don't know why the PCV would throw a code 34.

I used to get code 33 and 34 from my maf sensor now and then. It would come and go for no reason. Then I put a new battery in, and the SES light almost never (knock on wood) comes on any more. Go figure, huh ?

 

I'm assuming that it qualified as a vacuum leak as it was not making a tight seal. And I've read a lot of places that a vacuum leak could throw a 34. But I've thought I've had it fixed a number of times, so only time will tell.