I recently failed emissions. I thought it wouldn't be a big deal because I knew that my ignition system needed a little work. I did the work, and the car ran a lot better, but I still didn't pass emissions. I checked all of my temperature sensors, and they were fine. I had replaced my O2 sensor and my CAT 2 years ago so I wasn't worried about them.

I finally started reading through the factory workshop manuals, and what do I find to my amazement? The baseline mixture can be adjusted at the AFM (Air Flow Meter). It takes a CO meter to do it, but mixture is adjustable on our cars. This contradicted everything I had been told in the past .

I made an appointment with Motorsports International in Portland, OR. I had heard good things about them from several people. I chose to take my car to a shop for this item because it was cheaper than buying a CO meter.

Well, now my car passed with flying colors. I have about 1/3 of the allowable emissions. Incidentally, it runs better too! It runs great now. It sounds like and old american V8. Now it sounds like a new Boxster. Seriously.

I thought I would post this note because no where in the archives did I find mention of this adjustment.

 

Congratulations! Sometimes bringing your car into a specialist will save you a lot of time and aggravation with trying to do it yourself. So what were your before & after emmissions? What part didn't you pass? Could it be possible that a previous-owner had tweaked the AFM in an attempt to get better performance?

 

I was just barely failing.

Hydrocarbons
Allowable: 2.00
Had: 2.30
Now: 0.79

NOx:
Allowable: 3.70
Had: 1.70
Now: 1.60

CO
Allowable: 32.0
Had: 35.0
Now: 10.2

The guys at Motorsports International said that the mixture goes out-of-wack with age. I had the same suspicion as you.