Modern Vespa

part 1: (please read all 4 before replying)

since valentines day my scoot hasn't wanted to idle properly and I get P0130 errors (lambda) that sometimes clear themselves and sometimes I have to clear it. and sometimes it stalls.

but it does run well with a little throttle and cruises happily including reaching and holding high speeds on the freeway.

look at this graph of the bike idling on the stand, you can see the rpm rise/fall along with the fuel trim and lambda/o2 as it tries and tries. often this is cycling between 1600 and 2600. sometimes when the rpm drops it goes low enough to stall


crosslinks:
T̶h̶i̶n̶k̶ I've a̶l̶m̶o̶s̶t̶ worn out another throttle body
My new throttle body doesn't rattle. UPDATED: dying 🤬🤬🤬

part 2:
things tried (not in order)

new air filter (in Aus have corrugated paper not oiled foam)

new battery.

new lambda sensor + PADS by the mechanic.

new exhaust header (mechanic cracked it when replacing lambda).

valve check.

new spark plug (replacing the wrong one that the mechanic had installed).

fuel cleaner.

throttle body clean.

ecu reset (battery disconnect).

wiggling things.

spray a little engine starter around intake manifold etc to see if it reacts.

Lots and lots of searching and reading old posts on this forum.

inspected injector, with particular attention to it's o-ring


I have NOT touched the TPS.

Note: in Aus we don't have Evap canisters.

part 3
if I flick the throttle then the lambda does give plausible values so I don't think the lambda is stuffed

part 4
this is what it looked like last year when idling. ie, lambda and trim appeared to work resulting in stable rpm

Did you remember your scooter on Valentine's Day?

My 2006 GTS started doing what you're showing about 5 years ago. It still runs fine at speed but feels like the engine is loping at idle.

I just figured it was old age, like my dog pants more now as he gets older.

I'll follow this thread in case you find an easy fix.

It is an intriguing problem.
You seem to have quite sophisticated tools.

The aim of the ECU is to keep the combustion stoichiometric. Meaning oxygen in the exhaust should be zero. No excess and no shortage of oxygen.

In the 2021 data that is what is happening. Oxygen is fluctuating around zero and the idle is stable at appr 1700rpm, the normal idle.

What I find the major difference between your 2021 and 2022 readings is the lambda sensor volt reading.

In the 2021 readings it goes constantly up and down between 0,1 and 0,72V. That is what you expect from a feedback system: it constantly measures and reacts.

In the 2022 readings it is most of the time at 0,1 and makes sudden spikes when oxygen surplus reaches 40%. That is fundamentally different.

I expect the ECU reacts on the lambda sensor voltage, not on the 02% reading.

Why does the lambda sensor only reacts at these high levels of oxygen surplus?

The graphs etc are from
GUIDE: How to read Engine Fault Codes (OBD/OBD2)

Amusingly enough i was actually riding to see a girl* when this became bad.

* For work purposes not romantic 😭

Think you're reading it wrong (or i misunderstood what you wrote) ...

The second graph is the Fuel Trim, the third graph is the O2(lambda) Sensor. The fuel trim is that the ecu does in response to the O2

Note, low voltage means high oxygen (lean). Yes it's opposite to what you'd expect.

From Bosch The Modern Oxygen Sensor.

Is there a suggestion here?

I did read it wrong, correct. But my point remains unchanged: why is that lambda sensor reading (third graph) so different between 2021 and 2022?

well that is the question.

As I said above I don't think it's the sensor at fault (two reasons). My current suspicion is that it's an intake leak causing too much air to get in when the throttle is closed. Ecu then keeps trying to adjust the trim for that extra air but gives up and drops and tries again.

I was simply comparing this year's output to last year's output.

I didn't link to the document because although I have a file copy I can't find it on the interweb.

Make fun of me thats okay but what is lambda? Is that the fake meat i get on a Yero? If I go to wrong Greek resterant.

Surging at idle is a classic symptom of an air leak.

Yah, suspecting that.

Any tips on which bit is most likely to leak? Eg o-ring where fuel injector goes into manifold or rubber pipe between throttle body and manifold or gasket between manifold and head or ...

It's a sensor that measures the unburnt oxygen in the exhaust gasses. It's feedback to the vehicles ECU to adjust the amount of fuel injected and/or timing to maximise efficiency and performance.

If you live near a Shell station run the tank down and refill the tank with V-Power.

When this became a problem I had half a tank(95 or 98) that i had got in the country near the end of a long tour. Since then I've finished the tank and am 1/4 through the new tank (98) from my regular servo (caltex).

V-Power has all kinds of detergents and the like in it. Worth a tank once a year.
Lowered the idle speed on my bike (14,000 kms).

It's all about a system of elimination and doing the simplest things first.

Hello stellbytes i am having same issue, maybe intake leak, worst case scenary bad ECU

I've ordered an intake hose and intake gasket and am crossing my fingers that it's that simple.

Before l,you can do a vacuum test
I have allready change o2 sensor
But the voltage at idle is very low
I positive about an air leak that messes with air fuel ratio
But I am still looking for it, as you said Before can be injetor leak true the o ring

I checked that o ring and it seemed fine

I have search in all www, soo much people with the same problem..
Sunday i Will visit piaggio dealer and ask them if there is some update from piaggio!!!
Because this is a normal issue in newer engines

I know you said you cleaned the throttle body, but you didn't say anything about cleaning the idle air passage that the idle stepper motor controls. I was having very similar issues on my '07 GTS and found two things:

1) cracked fuel injector (at the connector)

2) I sprayed WD-40 through the idle air passage to clean it and get the stepper motor pintle to stop sticking.

#2 was contributing to the issue with the P0130 O2 code and erratic idle. Sometimes it would idle too high, sometimes it would stumble and die.

Also, in my case being a U.S. bike it had a canister, which had become fuel saturated and had to be disconnected.

Let me know if you have cleaned the idle air passage, and if you haven't yet let me know if doing so fixes your issue.

Steelbytes
I Will keep you updated! Please do de same
Like Bueller said clean idle bypass!!!
But your engine is diferent from 07 gts model
Please keep us updated!!
If i find something i Will let you know

Adding to what Znomit said:

The sensor measures the oxygen in the exhaust, not to maximise efficiency and performance but to allow the catalytic converter in the exhaust to neutralize unburnt carbon hydroxides and CO into innocent CO2 and H20 (water-vapour).

In order for the catalytic converter to do so there must be a perfect balance between fuel and oxygen entering in the engine. It is called a stoichiometric mixture https://en.wikipedia.org/wiki/Stoichiometry . And that balance is controlled by the Lambda sensor.

1. was the crack easily visible?

2. I did spray into the idle air passage from both ends extensively. why did you use wd40 and not throttle body cleaner? did you do this why the engine was running?

Check this post

https://cheekythoma3.wixsite.com/itsme/idle

already have. It's a very good article

WD40 to try to lube the stepper
Ideally there would be a way to cycle the stepper & assure smooth operation throughout it's range
It may do that when the key is on

When I stop the engine I can hear the stepper run for a half a second then about 2 seconds later again for half a second. Sounds like it's open/closing (or opposite) so I don't think it's stuck. but maybe it isn't doing so fully?


yes it would be ideal if I could trigger it to do this without starting the engine. PADS might offer a way (or iawdiag which doesn't yet support hpes)

I'm looking at your initial graphs and wondering if the idle is dropping off because of a voltage drop…which of course has nothing to do with the idle passage. The idle speed might be picking up after the voltage, suggesting a causal relationship….. Are you positive you have a good connection between the coil and the spark plug? The idle stalling I had on my Master engine turned out to be a loose connection on the coil side of the wire, which was difficult enough to get to that it was not at all obvious.

I would not use WD-40 as a substitute for throttle body cleaner in the idle air passage, and I don't think any lubricant is called for after cleaning. I believe you have to take the throttle body off to fully clean the idle passage in both directions. Just spraying stuff in one way while the engine is running doesn't hurt anything but isn't enough. But I don't think this is likely to be the source of the problem. If you can hear it operating on shutdown it's probably working.

Or have a tankful of V-Power?

Fuel does not go through the throttle body.

How can i be positive? I checked the connector at the plug end when I replaced it. Haven't checked the coil end apart from wiggling it a little, damn hard to disconnect it?

I presume the throttle body can get clogged due to air blow-by from the cylinder head getting recycled?

Looking down your list of items checked, have you removed the fuel injector and cleaned it properly?