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Intermittent mid-range misfire.

Revhead

Just got it firing!
Joined
Jan 20, 2017
Messages
8
Location
Picton NZ
I have a 2013 Stelvio NTX 1200. Recently the motor developed an intermittent misfire under acceleration.
The misfire would come in at around 3500rpm and disappear around 5000 rpm. The engine would then rev smoothly up to 8000.
I had my local Guzzi wiz check it out and found one of the coils was faulty. Replacing the coil and plugs seemed to remedy the fault allowing the motor to rev out smoothly for the next 100 kms until the problem of misfire returned, although more intermittent than before. Has anyone else experienced misfire problems like this?
I need to eliminate other causes before open heart surgery to replace ECU.
 
I had something very similar and it turned out to be the sidestand switch, if your problem was briefly cured by changing the coil then this is unlikely to be this n your case unless it was just a coincidence.

I had suffered it for a couple of weeks (in the rev-range mentioned above which was always when I was accelerating) when I noticed that the sidestand warning light would flicker at the same time. It was then just a matter of cleaning the switch with contact cleaner and it was fine. It did happen again much later and I cured it the same way.
 
I doubt if it was your coil to begin with.

More than likely, your spark plug boots had been improperly pulled off before and you may have a crack in the rubber where the plug is able to arc out against the engine block. It causes this intermittent symptom like you describe. There are tons of posts here about it you can search, but this one may be of immediate use to you. Good Luck!

https://www.guzzitech.com/forums/th...io-plug-caps-with-ngk-sb05e.10810/#post-82260


- Scott
 
I had something very similar and it turned out to be the sidestand switch, if your problem was briefly cured by changing the coil then this is unlikely to be this n your case unless it was just a coincidence.

I had suffered it for a couple of weeks (in the rev-range mentioned above which was always when I was accelerating) when I noticed that the sidestand warning light would flicker at the same time. It was then just a matter of cleaning the switch with contact cleaner and it was fine. It did happen again much later and I cured it the same way.
Thanks for this .... I will definitely check it out.
 
I doubt if it was your coil to begin with.

More than likely, your spark plug boots had been improperly pulled off before and you may have a crack in the rubber where the plug is able to arc out against the engine block. It causes this intermittent symptom like you describe. There are tons of posts here about it you can search, but this one may be of immediate use to you. Good Luck!

https://www.guzzitech.com/forums/th...io-plug-caps-with-ngk-sb05e.10810/#post-82260


- Scott
Sure enough, I can see someone (not me) has poked a hole into the spark plug boot. Looks like a screw driver has been used to pry up the plug boot. Thanks for the heads up on this issue.
 
So as my dash goes blank or inverts,
I'm going to replace plugs and caps as discussed in other threads on my 08 8v Stelvio.
Thought that I'd have a wee look at the side stand switch as well. How can you get it off? The back Allen bolt isn't really accessible. In the meantime I've sprayed it with Rockeze to make sure it doesn't stick.
I've sealed up the speed sensor so hopefully that won't be an issue.
Cheers
Min
 
After weeks of trying to track down my mid-range misfire, it appears the problem was a faulty crankshaft sensor. The sensor has been replaced and I have had a few thousand kilometers of no more misfire! Fingers crossed.
June 2019, Misfire returned after 250 kms. Took bike to CMG in Christchurch (the only Guzzi rep and new Guzzi dealership on the South Island). Left the bike with them for nearly 4 wks as they slowly worked through all the systems. A number of areas found faulty, loose battery terminals, crank sensor rechecked-clearance OK, Check throttle sensor, fuel vent line completely blocked, ignition system OK. Misfire disappeared for 2 days riding. Head lights not working, Generator found not to be working. Circuits and relays rechecked- find poor connection in a 5 pin relay connector. Rectify this fault which seemed to solve the misfire. Bike kept by dealer for another week who continued to test ride with no further faults or misfire.
Collected bike and proceeded to ride 340km home. 2 hrs from home stopped to pee. restarting engine I lost headlights and misfire returned. CMG mechanic picked up bike next day and spent the next 4 weeks doing the fine toothed comb search for the fault. Long story cut short the fault was tracked to a corroded alternator wire connection which was causing an intermittant misfire, no lights and flat battery. The wire connection is tucked behind the motor, rarely wet and quickly dried by cylinder heat. Since rectifying this corroded connection I have had 5000km of trouble free riding. My shaken faith in the Stelvio has been completely restored. I just love this bike, so under rated yet so capable. Keeps the smile on the face every ride.
 
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