2001 Accord: Stalls during stop

My Accord (2 door, 4 cyl, 2001, manual, 65,000 Km) engine occasionally just stops as I press the clutch to the floor (while coming to a stop).
This is happening about 1 in 20 stops; sometimes two or three times in a row and then doesn't occur for a few days. In any other state, behaves perfectly, accerated briskly and cruised without fault.
For example coming up to a stop/light I'm downshifting and compressing and as it comes to final rest, the RPM just decays right to 0. (Cluth all the way in). Occasionally, the RPM will go right down to 0 and then come up to 500 - 750 by itself, but usually the engine stops.
Sometimes the car will idle at 500 instead of the more normal 750-1000 range. During this low idle speed the engine will occasionally "tremble". Sometimes it will recover to 500 RPM after this, but usually just sits at 500 unless I give it a little gas.
Car always starts without fault or delay, so sometimes if it stalls even before a complete halt (say when a light goes green before full stop) I can re-start it by letting up the clutch in 2nd or 3rd / or simply start it with the starter while rolling.
I see another similar post referring to an "igniter" problem or ignition switch problem ... but it is not failing randomly, only when I come to a stop.
No "Check engine" light.
The mechanics at the garage where I changed the oil the other day had no idea (they did the usual checks and found nothing) and suggested as a minimum that I run a bottle of injector cleaner through the tank (and I'm doing that now...). Naturally, when the mechanic went for two drives in it, it behaved perfectly.
Also they said there is no gas filter, just a strainer at the gas tank. Is that correct?
Thanks, Alan
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