86 Tercel failing emissions control

I recnetly went through air care (emissions control) here in BC. My 2WD 86 tercel failed in that it had 2.5 times the number of hydro carbons allowed. Last 2 times I have done air care they have been under the allowable limit.

How can I figure out what causes the high hydro carbons. The only thing unusual with my car is that the weld that attaches my exhaust and muffler broke so I clamped it. I also cut my air conditioner belt as the air conditioner had seized and it was "squeling like a banshee".

I know it needs a timing belt, but I need to pass air care before I do that.

BOONER