Modern Vespa

After start my Vespa GTS 250ie has lower idle, also start is slightly weak, tacho shows rpm at 3 bars. Later after about 20 sec rpm goes up to 4 bars and will stay at this rpm all the time also during ride when I stop and let it idle. Absollutely no problem with idle rpm during ride, newer goes lower or vary, just stays on 4bars. Also when I start and there is low ide, then pull throttle slightly, rpm goes up and then dow to 4bar on tacho.
When I start engine with even slightly pulled throttle, start is much better and idle rpms are immediately at 4bars. Please do you have any suggestion how to adjust idle for engine start?
BTW, there is new spark plug, battery, air filter.
Thank you

I would look at the basics "Fuel-Spark-Air" = make sure that the fuel injectors are clean, spark plug is clean and wires are good, air filter is clean and intake path is clean.

There is an allen bolt on the throttle cable at the intake, but different opinions on adjusting this since it is controlled by the computer. Instead, cleaning out the throttle body would be my next step after the basics.

Also, the fuel pump tends to wear out over time, so if you are still having an issue then you could replace (it's a pretty big job). I was having some issues on my 2009 GTS I.E. and replacing the pump made a huge difference.

Three bars is proper warm idle, but I wouldn't trust the tach because it isn't accurate enough to see what's really going on.

Having said that it sounds like you have a vacuum leak that is making the idle higher than it should be when warmed up. Check the throttle body clamps, as well as the hose that goes from the throttle body to the canister.

Bueller has a good point for sure, given the age of the 250ie the hoses can easily break down causing a leak somewhere in the system.

Hello and thank you for your advices. Checked carefully hose from throttle body to air box and clamps. Everything is clean without damages and correctly mounted. Airbox is also clean and ari filter is new. Battery and spark plug is also new. Not sure if there can be any case in thorttle body, not sure how to check if works well or how to clean it. There should be baypass chanell with stepper motor to control air flow when idle. How to check if it works correctly?

Does the bike have a charcoal canister? Did you check the vacuum line that goes from the canister to the throttle body?

Also, you said it has a new battery. Have you ridden it enough miles for it to relearn idle? It always takes a while for my 250 to relearn idle after I've had the battery disconnected, and until it does relearn it tends to idle high. Usually a quick blip of the throttle will help settle down the idle.

If you want to look at how the stepper motor is operating you need to plug it in to software. There is a link on this website somewhere that tells you how to buy the parts for a diagnostic cable and links to free software. I have it all and it works great.

Robot just posted a video about this that may help. Looks like pinkscooter beat me to it.
Robots video on hidden air leak

Hi Uschak,

Ok, so this is a known issue with some GTS bikes. My own GTS300ie 2016 model also had this issue. It is it seems usually caused by the throttle position sensor not quite parking correctly when very cold and thus is out of alignment slightly for a near freezing cold morning start. At least that's what a Piaggio tech told me and I think he's right. Giving the bike just the slightest bit of throttle allows her to start normally under those circumstances. My bike behaved just like yours and was like it from new. It always started correctly with no throttle when the ambient temperature was a bit warmer. It ran fine all the time and never gave any issues.

So the cure appeared to be an ecu update. It was not a specific update to cure that issue, but a routine ecu update that was available for my bike at service time. Since I do all my own servicing I took the bike down to the workshop and the guys updated just the ecu for me. It cost me £42. But it's free if you have the bike serviced by them at the same time. Probably the same your side of the pond too. After the update I never had that issue ever again. I don't know if I was just lucky or if is was the update that actually did park the throttle position sensor correctly for cold starting. Anyway it's completely ok now. Good luck! Let us know if you get it fixed.