emissions problems - help?

[blw]

I have an 89 E30 convertible. It's failing California smog test (~300 hydrocarbons out the tailpipe once warm, limit is 120 I think), and we've tried most of the obvious things. The O2 sensor has been changed, the computer was swapped out, the various intake things have been checked.

The engine itself runs very clean when the O2 sensor is disconnected - 10-15 hc's (so little that I thought that perhaps the gauge was broken, but I don' tknow much about this stuff), but the O2 sensor is known good. (We put in a new one, and then swapped with a known good one from another car).

At this point what's left?

The engine is in good shape otherwise - good compression, doesn't leak or burn oil, etc.

[Despite MY location in Virginia, the car is in California at the moment, where it's been since it was new. I plan to drive it to VA in April or May and back again in October.]

[blw]

Aha! The answer in the back of the book for others in the future is that it was a (pair of) bad mass airflow sensors, combined with a weak catalytic converter. We'd tried another airflow sensor, but it was either maladjusted or just broken. When we put a new one in, the HC's dropped immediately. The cat is weak too, although it was not the major contributor to this particular problem.

[Jared at Pelican Parts]

I agree, I would think that the cat is blocked