I have a Bryant 397HAW036080 ACBA furnace that Short cycles.

When heat is called for the first time the main valve only stays open for a few seconds.

Inducer and blower continue to run.

The cycling continues with the MGV staying open for longer periods each cycle up to about 90 seconds when the house is heated enough to satisfy the thermostat.

It appears something is temperature sensitive either in the control board (fairly simple - 1985 vintage) or the gas valve itself is temperature sensitive.