sounds like the very short 30 second run- leaves unburned fuel in the cylinders.
when you start it-- do you start it- and while its revving high-- do you immediately put it into gear and move it-- and then shut off?
when its running at high idle- the vehicle is doing double injector pulses (running rich) to get fuel to help warm up the CATS.
next time you move it-- wait till the engine idle is down below 900.
(I actually dont move my car until RPMs fall below 1000).
when you start it-- do you start it- and while its revving high-- do you immediately put it into gear and move it-- and then shut off?
when its running at high idle- the vehicle is doing double injector pulses (running rich) to get fuel to help warm up the CATS.
next time you move it-- wait till the engine idle is down below 900.
(I actually dont move my car until RPMs fall below 1000).