I went Subie Ej22 motor 7 years ago to replace 1.9 WBX.  The "motor" was completely rebuilt, but the "ancillary" components were simply transferred over.  Among these was of course the Throttle Body and the Idle Air Control Valve.  Much gumminess.  Sticky even.  That causes intermittent issues like you are describing.  One afternoon of taking things out onto workbench, and much cleaning with Qtips and Carb cleaner and so forth, and things all became fine again.  Smooth idle, no stalling, improved numbers at Smog Test, better MPG, peppier performance.  Since you were asking for ideas....that's mine.  Gumminess doesn't fix itself, and a quick spray doesn't work..need to get down and dirty.
    On Monday, April 14, 2025 at 03:06:24 PM PDT, Mark McCulley <mark@markmcculley.com> wrote:  
 
 Hi Markus,

Your described symptoms are similar to what I experienced with my van about a year ago. The problem turned out to be the throttle position switch. This switch is located on the underside of the throttle body, it tells the ECU when the accelerator pedal is pressed (run state) and when it is not pressed (idle state).

Good luck!

-Mark

> On Apr 12, 2025, at 6:55 AM, Markus Benne <mbenne@m-bass.com> wrote:
> 
> My bus has developed an escalating issue where it it will bog while driving for a second, then keep going.
> This has been going on for about a year, but it is suddenly much worse, to the point of the car actually stopping.    Usually it will eventually restart and run fine for a little while before recurring.  Frequency is increasing.
> I needed a tow the other day for the first time, and I'm about to trouble shoot, but it was placed badly (couldn't open rear hatch), and although it started badly, it did start, and is now running fine.  Grrr.
> 
> 
> Exhaust isn't blocked as far as I can tell ie exhaust is coming out.Air filter seems ok.Fuel supply next I guess.
> Any input appreciated.