Black spark plug

[Vusette]

Hello,

I am new here! A Guzzi rider from Belgium.
I own a Breva 850. It covered 45000km's up untill now, without any real issue.
Only recently there is a strange problem.
At a certain point the engine started to develop a small misfire. Only from time to time, a small hick-up.
This hick-up is getting worse as the km's rise.
One morning the bike started on only one cylinder.
I removed the spark plugs an noticed that the left hand spark plug was completely black.
I fitted new plugs and the problem was over I thought, but after only 30 km's the problem came back.
Black left plug again.
The throttle valves are nicely adjusted, TPS is ok at 4.60.
I already swapped the coils and plug leads, all to no avail.
Fuel filter and air filter have been changed recently.
Now I am suspecting the injectors. Is it possible that the left hand one is staying a little bit open all the time,
resulting in a rich mixture?
I also must mention the fuel consumption. Normally the Breva needs between 5 and 6 liters depending on the
outside temperature and speed.
Now it needs 7 and more at moderate speeds and 13° c.
Anyone with constructive ideas?????

 

[john zibell]

You may be on the correct path. Check with some of your local auto shops to see who in your country or nearby cleans injectors. The stuff they add to the fuel just doesn't do the job properly. I know a good shop in the US, but there must be a few in Europe. You might want to check the web site of the US shop to see what they do for injectors.

http://www.rceng.com/Fuel-Injector-Clea ... essionID=6{zUH0fY1BFoTO6x4gDt

Let us know how you make out.

 

[Stevie]

I ran into that problem on my 13 Stelvio and finally deduced that the problem was a faulty O2 sensor after eliminating all the more obvious suspects you mentioned.

 

[john zibell]

I ran into that problem on my 13 Stelvio and finally deduced that the problem was a faulty O2 sensor after eliminating all the more obvious suspects you mentioned.

Possible as the 13 has two senors. The 850 only has one Lambda sensor so I think that would be less likely on the 850..

 

[GTM®]

Also, check the plug wire at the coil. Sometimes they work loose while servicing the bike and pulling the tank, etc.

 

[Vusette]

Yesterday I swapped the injectors and let the engine warm up to 60°c in the garage (as it was raining).
If the problem is in the left injector, the black plug should be on the other side now.
I didin't mention it before, but I have Guzzidiag software on my laptop. Very handy to do a TPS reset!
With that program I earlier got a fault reading nr PO201. According to the guzzi service manual this means a left side injector fault.
I errased the fault, but it kept coming back.
After the injector swap the fault did not come back, not even with the engine at operating temperature of 60°.
Was there a bad contact somewhere?
So now I am hoping...

Today is dry again and I intend to take the bike for a ride.
Fingers crossed !

Philip

 

[Vusette]

Hello again,

Yesterday I took the Breva for a spin.

I did a trip off 90kms. No more hick-ups!.
On arrival back home I chequed the plugs and now both were a bit to dark to my idea.
The central electrode had a reasonably good coulor but both side electrodes showed a very dark grey
deposit. Not black, but to dark. as if the choke was sticking on a carb. bike.
Anyway this is already an improval!
Now I thought, is it possible that the air-temperature sensor in the airbox is giving a too low temperature to the
computer, resulting in an enriched mixture?
To try this out, I now swapped the sensor form the Breva with the one from my Stelvio.
tomorrow: New test-ride!

Philip

 

[john zibell]

More likely the engine temp sensor is reporting a low temp. Get some thermal mastic and put it between the end of the sensor and cylinder. This improves the readings from that sensor. The air temp sensor doesn't play that big a role in the mapping. Use your software to see what the senors are reporting. Use your tools and don't just guess what is going on. If the sensors are within a few degrees of actual you are OK.

 

[Vusette]

The air-temp sensor is situated in the airbox, not on the cylinder.
With Guzzi diag you cannot really read out the sensors.
You only get faults or no faults.
I also agree that I should use my tools, but what if these tools give the all OK sign?
Then you only can make an educated guess...
I agree that the air temp is not that important but with the 6° temperatures we have here right now, the ECU seems
to find it necessary to enrich the mixture constantly.
I suppose it has been like that since the first day I had the Breva.
Normally I don't go around checking plug colours every 60 or 70 km's. And consumption has always been quite high in winter time. But as the hick-up problem forced me to start looking for some fault or problem, I want to go to the bottom of the problem now.
I now received a map from Paul with compensation for low temperatures.
He says the maps for 2-valve engines originaly have a to strong compensation for low temperatures.
By adjusting the compensation for low temps sveral other Breva and Norge riders got good results.
I will try this map as soon as possible. Possiblly this afternoon.

I will keep you informed,

Philip

 

[john zibell]

B)

The air-temp sensor is situated in the airbox, not on the cylinder.
With Guzzi diag you cannot really read out the sensors.
You only get faults or no faults.
I also agree that I should use my tools, but what if these tools give the all OK sign?
Then you only can make an educated guess...
I agree that the air temp is not that important but with the 6° temperatures we have here right now, the ECU seems
to find it necessary to enrich the mixture constantly.
I suppose it has been like that since the first day I had the Breva.
Normally I don't go around checking plug colours every 60 or 70 km's. And consumption has always been quite high in winter time. But as the hick-up problem forced me to start looking for some fault or problem, I want to go to the bottom of the problem now.
I now received a map from Paul with compensation for low temperatures.
He says the maps for 2-valve engines originaly have a to strong compensation for low temperatures.
By adjusting the compensation for low temps sveral other Breva and Norge riders got good results.
I will try this map as soon as possible. Possiblly this afternoon.

I will keep you informed,

Philip

If you get Centurion you can view sensor data in real time. I guess this an example of you get what you pay for. Again, the cylinder temp influences the map more than air temp, so that mastic will make a difference.

 

[Vusette]

Hi,

What is centurion?
What can you do with it an is it available for us europeans?
Philip

 

[GTM®]

Philip, it is shown here; http://guzzitech.com/store/product/15-t ... pathway-11

Q&A here; http://guzzitech.com/forum/160/1676

You can write me direct with any other questions. I ship worldwide.

 

[Brian UK]

As has been said above, you should be looking at the cylinder temp sensor mounted on the inside of the RH cylinder head, not the air temp sensor on the airbox.
Remove the sensor and fill the cavity it goes into with a heat conducting mastic. This will ensure that the sensor accurately reads the correct cylinder temp. Otherwise it tends to read a lower temp than is actually there which will result in a richer mixture.

It is also possible to add a 20k ohm resistor across the sensor terminals (ie in parallel) which will make the eCU think the engine temp is higher that it actually is. This only affects things at low temperatures due to the non linear response of the sensor.

I have the earlier version of Centurion, VDSTS, and with that I can read what all the sensors are telling the ECU.

 

[Vusette]

Today it was raining cats and dogs, so the bikes stay inside!
I lifted the Breva's fuel tank a little bit to be able to give the engine temperature sensor a glance.
First I tried to disconnect it, but the connection is an unknown type to me.
I thought it would be something like the connectors on the injectors (you have to push the wire spring).
but this seems to be something different. How does it come off?
In a clear moment, I decided to fit a spanner on the sensor and I could screw it in more than a complete turn.
It wa actually only hand-fast.!
Possibly this can have caused a low temperature reading?

Philip

 

[john zibell]

Today it was raining cats and dogs, so the bikes stay inside!
I lifted the Breva's fuel tank a little bit to be able to give the engine temperature sensor a glance.
First I tried to disconnect it, but the connection is an unknown type to me.
I thought it would be something like the connectors on the injectors (you have to push the wire spring).
but this seems to be something different. How does it come off?
In a clear moment, I decided to fit a spanner on the sensor and I could screw it in more than a complete turn.
It wa actually only hand-fast.!
Possibly this can have caused a low temperature reading?

Philip

Older version of the connector you pushed the wire at the center to release it. On these new ones, you have to carefully release the wire clip to remove the electrical connector. Only being hand tight isn't the issue, you are luck there. Be sure to use the mastic. Then just snug the sensor down. If you try to get it tight, you can bread the plastic holder. Then you have a real problem.

 

[Vusette]

Hi,

Last thursday I had the injectors cleaned by a profesional company.
They are both clean now. The mecanic told me however that there is a difference in the way they were working.
One is working normally, the other one is "spraying" a little bit too wide. But he wasn't sure this would be the cause of my
hick-up problem.
l also isolated the enginetemp sensor (as an experiment) with a bit of isolation tube that is normally used
for isolating water pipes in and around the house.

The result?
Engine is running wonderfully and the average consumption has gone down to a normalish 5,8 liter.
I am waiting now for a bit of nice weather to do some more km's.

Philip

 

[john zibell]

Good idea insulating the sensor so it doesn't cool while running. I'll need to remember that. Adding the mastic at the probe end would probably make it even better.

 

[Vusette]

Hi,

The Breva soap continues.

I have re-syncronised the throttle valves. There was some difference.
I also tried a new engine temp sensor. My dealer was so kind as to lend me one. no result.
I swapped the lambda sensor with the one on my Stelvio. no result.
In Guzzi diag everything seems ok. Lambda working, Stepper working.
I have the standard map in the ECU with the lambda set to "on."
With Guzzi diag you can switch off the Lambda. This makes it even worse. So I keep the Lambda to "on".
Today I went for a ride. After 20 km's the engine started to misfire from time to time.
It feels as an engine with a sticking choke lever.
The problem is at its worst between 2000 and 3000 rpm. When this occurs, the fuel consumption rises alarmingly.
Once you reach 4000 the problem almost completely disappears.
Now both spark plugs are black! At least this means that syncronisation is ok.

Back home I pulled the rubber hose that connects the airbox with the stepper and plugged it.
I went for a short ride again (time was running out) and the bike was a whole lot better!
No more misfires, only a small irregularity between slowrunning (now at 900 rpm) and 1500 rpm.
Probably because of the no longer working stepper.
Can it be that the stepper is sticking from time to time and thus causing the misfires?

Philip

 

[Roblatt]

The problem is at its worst between 2000 and 3000 rpm. When this occurs, the fuel consumption rises alarmingly.
Once you reach 4000 the problem almost completely disappears.
Now both spark plugs are black! At least this means that syncronisation is ok.

Back home I pulled the rubber hose that connects the airbox with the stepper and plugged it.
I went for a short ride again (time was running out) and the bike was a whole lot better!
No more misfires, only a small irregularity between slowrunning (now at 900 rpm) and 1500 rpm.
Probably because of the no longer working stepper.
Can it be that the stepper is sticking from time to time and thus causing the misfires?

Philip

Philip,

I have the 1100 Breva which is essentially the same motor. Now I'm not mechanically minded, but, is it possible you're not revving the engine hard enough? Anything below 3000rpm and mine runs like a dog. I usually run in the high 3's to low 4's. I haven't had a problem in 75,000km.

Just a thought . I'm happy to be corrected by the more learned here (just about every one)


Robert

 

[john zibell]

Hi,

The Breva soap continues.

I have re-syncronised the throttle valves. There was some difference.
I also tried a new engine temp sensor. My dealer was so kind as to lend me one. no result.
I swapped the lambda sensor with the one on my Stelvio. no result.
In Guzzi diag everything seems ok. Lambda working, Stepper working.
I have the standard map in the ECU with the lambda set to "on."
With Guzzi diag you can switch off the Lambda. This makes it even worse. So I keep the Lambda to "on".
Today I went for a ride. After 20 km's the engine started to misfire from time to time.
It feels as an engine with a sticking choke lever.
The problem is at its worst between 2000 and 3000 rpm. When this occurs, the fuel consumption rises alarmingly.
Once you reach 4000 the problem almost completely disappears.
Now both spark plugs are black! At least this means that syncronisation is ok.

Back home I pulled the rubber hose that connects the airbox with the stepper and plugged it.
I went for a short ride again (time was running out) and the bike was a whole lot better!
No more misfires, only a small irregularity between slowrunning (now at 900 rpm) and 1500 rpm.
Probably because of the no longer working stepper.
Can it be that the stepper is sticking from time to time and thus causing the misfires?

Philip

Did you ever check to see if the readings form the engine temp sensor are in range? Just because you tried another one doesn't mean you are getting accurate readings.