I have owned a 1993 2.0 fuel-injection Honda Accord Coupe for 11 years and it has always run very smoothly. However, after being off the road for 3 months last year, while waiting for some replacement parts, it has been consistently running unevenly from cold starts. It still drives well, but the idle speed on automatic choke (previously steady at just over 1k revs) now continuously fluctuates rapidly between 1k and 2k rpm. After about 10 minutes, when it's warmed up and come off automatic choke, it reverts to the normal, steady idling speed of about 800rpm.

I have consulted a couple of local garages, one of which specialises in classic cars and they suggested that it was probably a temporary problem due to the car's period of inactivity. Possible causes were thought to be either a sticking valve or partially blocked fuel pipe. One solution could be to use an additive to clean the fuel (injection) system. As I generally only use the (low mileage - 96k) car about twice a week for relatively short journeys, it might also benefit from a longer motorway journey at a consistent high speed.
I would very much appreciate any insight that you may have on this relatively minor, but slightly irritating, problem.