95 DX fail CA Smog. What's wrong?
 

I have a 1995 California Honda Civic DX with 1.5L 4 Cyl D15B7 (223,000 miles). It failed test 1, with only hydrocarbons too high. [118 ppm instead of 68ppm at 1702 rpm/15mph and 61ppm instead of 44ppm at 1914 rpm/25mph]. Engine timing was 15 degrees.

I checked my records and noticed that oxygen sensor had not been replaced (at least since before I got the Civic at 107k miles). The old sensor was a Denso 234-2311. The NEW ONE is 234-4009. The Denso website says that is the right one. 234-2311 doesn't show up anywhere, except for a badly-spelled Asian website.

At 179k miles, the car got a new timing belt, water pump, tensioner, spark plugs, wires, rotor, cap.

I also:
1) replaced air filter (old filter was pretty clean).
2) looked at spark plugs.- 2 of them were slightly loose. One had a screw-on nubbin (that the wire slipped onto) that wouldn't tighten, like it was stripped. I found another nubbin in the spark plug locker that screwed on tightly.
3) remove AC compressor, radiator and fan, wiring harness, piping across the front of the car. Some piping and the internal radiator are still in place. The AC system was empty of refrigerant when I got the car.
4) checked and adjusted valve rocker arm clearance slightly
5) change oil and filter
6) check compression: cylinder 1:135, 2:135, 3:143, 4:146 (it spiked higher)
7) check PCV valve (works)

Twice after replacing the oxygen sensor, the check engine light came on temporarily. I treid to get a code (put clip across the connector), but got nothing.

Hoping for a little improvement, I had the car smogged again. Bad news. Now I was a gross polluter. Engine timing was only 8 degrees. At 25mph, HC was up to 283ppm, and all the numbers were worse. For example, CO rose from 0.12 to 4.15.

I went home and checked the timing with a timing light, and it was 15 or 16 degrees. I had holes in the muffler and midpipe, which I taped up before getting the smog checks. I just installed new ones.

Could removing the Air Conditioning possibly hurt? What would make the timing change from 15 to 8 degrees during the second test, but be back at 15 later? Could the terrible performance during the second test be related to the wrong engine timing?