I have a 1986 Corolla (FWD, 4AC engine) with 50K highway miles (all mine) that over the past few months has gradually become harder and harder to start, hot or cold. It always cranks fine but either dies right away or chugs and gradually increase in RPM.
I've checked for vacuum leaks and gone through the factory manual's procedure for checking the emissions and fuel systems, except for the tests requiring high altitude or temperature below 45F. I also checked the carb adjustments (choke opening, base and other idle speed). The AAC diaphram doesn't leak. The fuel solonoids click when voltage is applied directly to them. The choke mechanism doesn't bind, and the choke seems to open gradually as the choke spring uncoils. Acceleration is fine, hot or cold, at least as well as can be expected from 75 HP.
A year ago I changed the plugs (NGK), vacuum hoses (all Toyota), and had the engine checked (175 PSI, 5% leakdown). Oil consumption is better than a quart per 5K.
What could be the problem?