Modern Vespa

I've posted a few times with troubles on my 2018 Liberty 150. She runs great when warmed up, but starting can take a couple attempts first thing in the morning and sometimes she idles rough if the engine hasn't warmed up and can even stall.

I've done just about everything to this thing... plug, valves, filter, removed and cleaned injector, checked fuel pump, cleaned throttle body, replaced engine temp sensor. There's no check engine light.

I actually don't mind it too much taking a few 1-2 sec attempts to start, but if I drive a tiny way and then go back to idle (like at a stop sign), it can just stall. It'll start instantly back up every time. Then, get 1/2 mile or more (engine warms up), idles beautifully on-going. Obviously a cold day it might be more like a mile.

I felt like maybe it just wanted to run too lean, so I picked up a lambda emulator to run a bit richer from scooter parts . I'm not seeing much impact on my issue, though might notice a little performance bump.

It felt worse today but I did gas up. Maybe there's something with the evap system? I know the previous owner had it sit a lot with bad gas in it. I think it's a stretch but thought I'd post one more time for ideas. All I could think of this point is hearing some ppl disconnecting that fixed things. I'm just not sure if it idles and runs fine warm that evap could be the issue.

Appreciate any thoughts as always.

I don't see mention of checking voltage while idling both when it's happy and when it's grumpy

I did put in a new battery and I've measured it to be sure it's staying charged. By measuring voltages, are you just meaning checking the voltage off the battery when it's just started? And if so, am I just checking if it's sagging?

The purpose is to see if the regulator is putting out a suitable voltage. So stick ya multimeter on it and see what it says while running.

I'm having the same exact problem with my liberty, if it's hasn't been run in a few hours, after the first start it stalls when I reach the first stop sign 200 ft away. Runs fine after restarting. Did you figure it out?

I had a few things going on since the old owner had some bad gas in there. So, I think my fuel filter change, cleaning the injector, and spark plug swap were helpful.

But, after much frustration, I finally caved and brought it to the dealer.

They found a code on the throttle body (that doesn't trip the check engine light), which led the mechanic to recalibrating the TPS (throttle position sensor) and doing an idle re-learn after that did the trick.

Those things you can't do without dealer tools, and did the trick. I think he charged me 2 hours of labor because he checked valves and a few other things along the way.

Runs perfect now, starts right away and doesn't stall anymore.