Modern Vespa

Hey all,

Got my Piaggio MP3 500 LT Business last year and absolutely loving it!
As it had some jerking when starting from stand still, I've immediately replaced belt and weights to Dr.Pulley 19g and it's best "mod" I've done to it. Lost some end speed, but gained so much for acceleration and it's way less jerky when starting.

But unfortunately since then, I've been having issues with check engine light coming on and off - and I don't think it's related to the new pulleys, but something else which I unfortunately can't diagnose..

Scooter runs perfectly, top speed 140km/h, reaches it pretty easily and it's quite reactive on the throttle. But when I'm idling at the same speed for ~30 seconds (doesn't matter if it's 10km/h, 30, 50, 100) check engine light comes on. It also comes when I start the engine and let it get warmer a bit, check engine comes on. (or when waiting on a red light)

To turn it off, it's literally a matter of slightly twisting the throttle or releasing the throttle. So either going from 50km/h to 40 or to 60, it would turn it off.

Did anyone ever have issue like this or has some ideas on what could be causing this?

I've replaced air filter, spark plugs, oil in engine, checked coolant, but that didn't resolve the issue.

Thanks all!


EDIT: Oh and forgot to add, checked voltage regulator, seems fine. 14.4V was highest I could catch while almost at full throttle.

Hi, any tips?

Have you replaced the oxygen (lambda) sensor?

throttle body cleaning?

Double check to make sure there's no false air being sucked in through the airbox/intake

knowing the dtc code would help.