Does anyone know why my bike is doing this?

[Huzo]

The thing I see here over and over, are descriptions of anomalous behaviour that raise more questions than they attempt to answer.
When a bike is “idling poorly”, that raises the question…(s).

Is it idling correctly and dropping one cylinder momentarily ?
8 stroking due to excessive richness ?
Interruption to electrical supply?
“””””””””””””””””fuel supply?
Sticking valve(s) ?
And on and on……

I see that your left plug is darker, that to me suggests that excessive fuel is being supplied to that cylinder but it is (partially) burning it.
If the spark was failing, the plug would be wet, not black….sort of…
Also, although none of us would deny the need for a decent spark, once the microsecond of spark has come and gone, it’s the flame front that continues to promote the combustion.
A bit like lighting a wildfire with a small match or a large one, once you’ve started the fire it’s irrelevant how big the ignition source was…
I’d be looking at a malfunctioning injector.

Also, after watching your video..
Had you not pulled the camera back for a second or so, I’d have gained the impression that you were blipping the throttle.
Are you certain the idle is not controlled by a stepper ?
Notwithstanding any of the above. It’s highly significant that on a STB motor, you have differing combustion on either side.
I would not go for an air leak issue, or one plug would be good and the other one white (lean).
I’d be further tempted to swap the injectors over to the other sides and see if the dark plug moves to the right side, but do not swap the pugs. It will be worth seeing if the dark one cleans up and the good one goes black.

[centauro]

And, I would not change the FI map until the problem is resolved first. Changing the map would not fix the issue; in fact, it would make the problem worse and harder to diagnose, with lots of head scratching and frustration.
Are there any vacuum hoses on the intake manifold that may be disconnected, damaged, etc.? Or a manifold gasket that does not completely seal?
Both cylinders seem to be firing, so, I would not suspect the plugs or plug wires to be the culprit.

[Tom]

+1  Reason for my comments before on an Italian tune-up.  Maybe the injectors need a cleaning.

[Huzo]

Or a manifold gasket that does not completely seal?

It’s a single throttle body, so that would affect both sides.
Even if it was the manifold gasket leaking, that would send it lean.

BTW.
Of the two plugs, which one is considered “normal” for gentle running ? I’m starting to wonder if the dark one is running ok and the light (right) one is failing from fuel starvation. When your bike quit suddenly at idle, it sounded like starvation.
Swap the injectors side for side and re check the pugs.
Also.
When the bike is surging from cold, put you hand on both headers and ascertain which one is “laying down…”Do some definitive diagnostics.

[Kev m]

I am nowhere qualified to offer any advice, since I have never owned any fuel injected bikes, but the fluctuating idle on any engine is usually associated with an air intake leak.
The ECU would then try to boost the fueling to compensate for the extra air going in. The sudden acceleration may be happening because, after parking the bike for awhile, the motor has cooled enough for the ECU to command a higher idle speed to warm up the motor. From the video, I can see that when the idle speed fluctuates, and throttle is applied, the response is very sluggish, typical of a very lean condition. The plugs appear to reflect this, as they are overly clean at the tips, at least one of them.
Could there be a crack or somewhere on the intake manifold where extra air is being sucked in?

Thing is, if it's like mine. It runs golden, almost perfect 99% of the time. It ONLY does it on some completely cold starts, for me, IIRC more likely in hot or humid conditions. And it only lasts for warmup and goes away within minutes.

Now I guess a mechanical air leak that only showed when it was say cold enough might make sense, except that I'm pretty sure mine occurs more often when ambient temps are hot.

Still it's a good suggestion if we can figure out why a leak might surface only once in a very long while.

[Kev m]

Are you certain the idle is not controlled by a stepper ?


Notwithstanding any of the above. It’s highly significant that on a STB motor, you have differing combustion on either side.
I would not go for an air leak issue, or one plug would be good and the other one white (lean).

See links I posted earlier it's a settled matter, the throttle body uses an integral stepper.

And as for air leaks, in theory I guess one could occur at the runner for that cylinder and not affect the other cylinder.

On the plugs, I'm not sure of the significance. EFI motors can go pig rich or crazy lean at the drop of a hat and plugs don't necessarily clean themselves of that. I was always told nothing but a plug chop can really tell you anything shy of the obvious (wet or oil fouled).

Of course the individual injectors and O2 sensors do mean there is some independent fueling so it is possible for one to run rich and the other lean relatively speaking. I'm just not convinced what we see is of any concern or causing the symptom.

[Huzo]

Thanks Kev.
So disarm the stepper and see what happens.

[lucky phil]

Thanks Kev.
So disarm the stepper and see what happens.

If you do this it will almost certainly throw a MIL and won't idle.

Phil

[Huzo]

If you do this it will almost certainly throw a MIL and won't idle.

Phil

Well, leave it hooked up to the electrics and just plug the vacuum. The stepper will be oscillating, but won’t affect the idle mixture.

[lucky phil]

Well, leave it hooked up to the electrics and just plug the vacuum. The stepper will be oscillating, but won’t affect the idle mixture.

The stepper is basically an ecu controlled idle air bypass valve. If you disconnect it then you have no idle control. With the single TB fitted I dont believe you can plug anything as it's all internal to the TB. The stepper "may" default to it's last position when disconnected, not sure.

Phil

[Huzo]

The stepper is basically an ecu controlled idle air bypass valve. If you disconnect it then you have no idle control. With the single TB fitted I dont believe you can plug anything as it's all internal to the TB. The stepper "may" default to it's last position when disconnected, not sure.

Phil

True, you will have no idle control while conducting the test, but you will either eliminate or highlight the stepper as the cause.
If the idle fluctuations disappear, then you know it was the stepper.
If it is all internal as you say unlike the big blocks…? Then either walk away or find the port that supplies the air bleed and disable it.
The whole aim is merely to see if it’s the stepper commanding the fluctuation.
When our OP’s bike quit at idle, it quit on both….(I think..)

[Kev m]

Ok, a couple of things.

* The stepper doesn't effect mixture per se, it effects volume. It's about increasing the amount of air and therefore idle speed so the engine doesn't stall on cold idle from too low an rpm. Mixture is still controlled by the ECM.

* You can't unplug it since it's internal. Guess you could find and block the idle passage as a test. But all that would do is confirm the hunting on cold starts is being caused by the ECM controlling the stepper and not WHY it is controlling it in that fashion (and we're 99.99% sure that's the case now).

* Maybe the biggest difficulty in troubleshooting this is the extreme intermittent nature (only happens during some cold starts) and once warned goes away completely.

Which is why after pursuing for a while nearly 10 years ago I said "screw it, I'll just let it warm up when it happens".

[redhawk47]

I had a problem with my V7II - occasionally running on one cylinder.  The cause of that could cause the problem you are having.
Cause: the fuel injector was plugged into the harness but the retaining clip was not properly installed.  As a result it would occasionally lose connection and lose power.  If that is happening on your bike it is then trying to recover by over-revving.

[stubbie]

Googling around points to bad O2 sensor or EVAP leak. Symptoms of EVAP leak are surging/stalling while driving.

[Huzo]

The stepper doesn't effect mixture per se, it effects volume. It's about increasing the amount of air and therefore idle speed

If the amount of air is being varied in isolation, then the air/fuel ratio (mixture), is changing as a function of the volume.
But rest assured, altering the volume of air and leaving the fuel flow static, is commanding the mixture.

[Kev m]

If the amount of air is being varied in isolation, then the air/fuel ratio (mixture), is changing as a function of the volume.
But rest assured, altering the volume of air and leaving the fuel flow static, is commanding the mixture.

Why would you assume the injector pulse width is static?

The same ECU that controls the injector pulse width is also controlling the stepper.

That's why I said "per se" the purpose of the stepper isn't to vary mixture, it is to control the volume entering past the plate and in doing so control speed. It's not to dilute the mixture.

[Huzo]

Why would you assume the injector pulse width is static?

The same ECU that controls the injector pulse width is also controlling the stepper.

That's why I said "per se" the purpose of the stepper isn't to vary mixture, it is to control the volume entering past the plate and in doing so control speed. It's not to dilute the mixture.

Ok Kev, the first statement was a bit of a word salad but yes, I see your assertion.
Enquires have been made….

[lucky phil]

Ok Kev, the first statement was a bit of a word salad but yes, I see your assertion.
Enquires have been made….

Have a think about this. The injector pulse width is controlled primarily by 2 things, TPS angle and rpm with a bunch of trims added to that. So if the stepper opens and the rpm goes up even with the TPS static the pulse width will change because the RPM increases.

Phil

[Huzo]

Well I have had a think since you asked me to.
The pulse width determines the amount of fuel per squirt I guess. That amount is determined by the needs of the engine at that moment and you’ll be bound to admit that the need is a function of rpm and throttle setting…
So.
Just because the revs increase, it does not mean that it is demanding more fuel.
Going downhill at 5000 rpm is using a lower throttle setting than going uphill at 3,500.
So linking fuel flow to rpm solely is not a legitimate line of thought…?

[lucky phil]

Well I have had a think since you asked me to.
The pulse width determines the amount of fuel per squirt I guess. That amount is determined by the needs of the engine at that moment and you’ll be bound to admit that the need is a function of rpm and throttle setting…
So.
Just because the revs increase, it does not mean that it is demanding more fuel.
Going downhill at 5000 rpm is using a lower throttle setting than going uphill at 3,500.
So linking fuel flow to rpm solely is not a legitimate line of thought…?

Who said the demand or fuel flow increased?. The needs of the engine are determined by the guy that writes the map in reality that's why there are good and bad maps. Some map writers determine badly. Then that's enhanced by the trims. Here's a fuel map for a Centauro, note the pulse width reduces as the revs rise and the throttle angle stays the same for the majority of the map. The original point is the fuel flow changes with rpm in isolation so if the stepper motor creates greater rpm without obviously changing the throttle angle then the FF will change also. That last statement is an overreach in reality as I dont actually know if the systems that use a stepper actually have a link between fuel and stepper position. I'm hanging my arse out there in the breeze:) 




Phil
 

[Huzo]

I’m leaving this alone now because it’s contaminating the thread.
Maybe one day we’ll pick it up, too hard on here.

[tris]

........

As for spark plugs, no, the gap is not in the code. The code is strictly about heat range (length of insulator), thread diameter, whether it's a resister plug or not etc. .....

Kev I wouldn't normally disagree but in this case the CPR8EB-9 plugs are special

Go here https://online.flippingbook.com/view/17923346/4/   Page 4

Where it says if marked -9 they come gaped at 0.9mm (no marks is 0.7 - 0.8mm)

That being said My V9 manual says it should be 0.7mm IIRC, which puzzles the heck out of me as to why MG buy a plug from NGK gaped at 0.9mm

I'm sure that the chap on the shop floor building the bike isn't re-gaping all the plugs 


-

[Kev m]

Well I have had a think since you asked me to.
The pulse width determines the amount of fuel per squirt I guess. That amount is determined by the needs of the engine at that moment and you’ll be bound to admit that the need is a function of rpm and throttle setting…
So.
Just because the revs increase, it does not mean that it is demanding more fuel.
Going downhill at 5000 rpm is using a lower throttle setting than going uphill at 3,500.
So linking fuel flow to rpm solely is not a legitimate line of thought…?

To clarify pulse width = time = the total amount of times the injector is actuated for a given intake cycle. Injectors don't just sit open, they are rapidly opened/closed to spray fuel.

Your logic is slightly faulty logic because you focused only rpm changing in your example but forgot the throttle changed too. So it's not the same as an example when the throttle doesn't change but rpm does.

Fuel is linked to speed/density - to rpm and throttle position and a change to one will change it, though I think throttle has a bigger effect. Either way, fuel is a function of both, a table of varied values based on the intersection of the particular row/column right?

If you close the throttle you've changed a variable (shifted one row or column). So going downhill with a closed throttle at 5000 rpm puts you on a different place on the table than going downhill with the throttle OPEN at 5000 rpm - that would have a lot more fuel.

Closed throttle and running at say 2000 rpm vs 1000 rpm there is going to be a little more fuel at the higher rpm, again two different places on the table.

[Kev m]

Who said the demand or fuel flow increased?. The needs of the engine are determined by the guy that writes the map in reality that's why there are good and bad maps. Some map writers determine badly. Then that's enhanced by the trims. Here's a fuel map for a Centauro, note the pulse width reduces as the revs rise and the throttle angle stays the same for the majority of the map. The original point is the fuel flow changes with rpm in isolation so if the stepper motor creates greater rpm without obviously changing the throttle angle then the FF will change also. That last statement is an overreach in reality as I dont actually know if the systems that use a stepper actually have a link between fuel and stepper position. I'm hanging my arse out there in the breeze:) 




Phil

Ha ha - great post. It reminds me that even thinking about this in two dimensions allows us to oversimplify.

If I'm reading that map right it looks like that map actually leans the mixture as rpm goes up if the throttle angle remains the same.

What it doesn't tell us is how rich it is to begin with, and why it leans. Isn't the hottest/strongest mixture point generally leaner than stochiometric? Does this map run richer at lower speeds to reduce temperatures?

And how is this map effected by correction factor for temperature, the OPs condition is cold idle right? Warm up gets a richer mixture based on cylinder head temp.

[Kev m]

Kev I wouldn't normally disagree but in this case the CPR8EB-9 plugs are special

Go here https://online.flippingbook.com/view/17923346/4/   Page 4

Where it says if marked -9 they come gaped at 0.9mm (no marks is 0.7 - 0.8mm)

That being said My V9 manual says it should be 0.7mm IIRC, which puzzles the heck out of me as to why MG buy a plug from NGK gaped at 0.9mm

I'm sure that the chap on the shop floor building the bike isn't re-gaping all the plugs 


-

Thanks for the correction and education. I missed that -# in the tables I've looked at in the past!

Cheers!

[Huzo]

No I don’t Kev, but it’s just too damn hard to keep on correcting people who unintentionally misrepresent what I say.
So, have a nice day…

[Kev m]

No I don’t Kev, but it’s just too damn hard to keep on correcting people who unintentionally misrepresent what I say.
So, have a nice day…

I'm not intentionally misrepresenting anything.

If you think that, then I don't know what you mean (whether that's my misunderstanding or your not expressing it well, could be two peoples divided by a common language).

Did you get my point on closed throttle vs. open throttle at same RPM = different fuel and why?

And how that is different from same throttle and different rpm?

And how temperature and cold starts also changes the equation.

And any other logic in any given map we don't know about/haven't considered yet?

[Huzo]

Ok, I swore I wouldn’t do this but anyway.
Whatever the stepper does or does not do, is not where I wanted to go. I was just speculating that the stepper may be not smooth enough in it’s operation and failing to make the miniature adjustments required to stabilise the idle.
All I wanted was to get to the bike while it was hunting and disconnect the stepper and see what if any, the immediate effect was.
If the symptom immediately alters, then it’s the stepper.
What then…?
Dunno.
But it’s targeting the cause.

[Kev m]

Ok, I swore I wouldn’t do this but anyway.
Whatever the stepper does or does not do, is not where I wanted to go. I was just speculating that the stepper may be not smooth enough in it’s operation and failing to make the miniature adjustments required to stabilise the idle.
All I wanted was to get to the bike while it was hunting and disconnect the stepper and see what if any, the immediate effect was.
If the symptom immediately alters, then it’s the stepper.
What then…?
Dunno.
But it’s targeting the cause.

Copy that.

Agreed that's logical and good troubleshooting.

Unfortunately not practical since it's integrated and there's no connector to unplug.

I will note that I had some Guzzi gurus think/troubleshoot this 10 years ago when I discovered it on my 2013 and because it was somewhat intermittent (seemingly but not verified that is varied with ambient conditions), but then went away completely within minutes (after warmed a bit) we gave up and moved on.

My bike does this on most cold starts to this day, and then runs flawlessly the rest of the day (unless I stop long enough for it to cool significantly, and then it's just another 3 minutes or so till it's gone).

Now why the OPs does it much less often? Ambient conditions might be it, or it might be a different unrelated fault, maybe a loose connector, but that doesn't seem to fit my pattern.

[tris]

Work with me a bit

I've just reread this thread and listened to the engine running at part of me says if a carb engine was doing that I'd adjust the idle mixture screw until it didn't.

Obviously we can't do that ourselves with these bikes,  idle is controlled by the ECU with the stepper adjusting the air to achieve the target idle

If the stepper was faulty,  then it might manifest itself as a hunting idle .

Does GDiag allow you to stroke the stepper on this ECU as you can on the CARC bikes?

Might eliminate the stepper if it does