Hello

My patrol has started to idle high, it back fired on fuel last night, and since then it holdes 1800-2000 rpm all the time got or cold. Started it up this morning and it holds 1200-1800rpm and won't go down after warming up.
What could this be and is there a solution, from what iv read the tb42 has a few problems with the auto choke ?

Any help would be appreciated

Thank you for your time

Marti