I have a 2004 Subaru Forester XS (manual transmission). A few times a month, the engine will not start or idle without feathering the accelerator. During normal driving, everything works fine until I press the clutch in or put the car in neutral. It feels like there just isn't enough fuel being fed into the engine. Most of the time, though, I have no issues. This issue has appeared and disappeared for a couple of years now. It happens in hot summer weather and in the dead of winter. It happens when the car has been sitting for a day or two, and it happens while I'm out and about.
I pulled out and cleaned the idle air control valve as well as the air intake system. I have used a couple different kinds of fuel injector cleaner. I checked for vacuum leaks. The timing belt was changed recently, and they checked the fuel pump while they were in there and said it was fine.
Any ideas? Maybe something I should double-check or test more thoroughly? It is more of a minor inconvenience than a catastrophic issue, which is why after a couple of years, I still haven't fixed the issue. Whenever it happens, I just give it some gas as I'm starting it and when the engine isn't in gear, and it works fine.