Hello,

my 2002 Sienna suddenly starts having difficulty starting. Everything sounds right except the engine dies immediately at start unless accelerator is pressed. It runs otherwise fine.

Where should I look into first? The fuel filter, or battery or, fuel pump, or idle-speed setting?

many thanks for any insight!

My 2002 Sienna had the same exact issue.
The symptom is caused by a faulty ISCV (Idle Speed Control Valve).
After replacing ISCV, idling was back to normal. The part costs about $50.

I had the same issue with a 1996 Camry, twice.

it is the idle air control valve that needs replacing. about $200 for the part. and while you got this out you might want to replace the rear spark plugs which are easier to get to with this part out.