Running on 1cyl after warming up

[Pedro Santana]

Good morning dear guzzi mates,

Will need your expertise, if i may:

Today on my way to work, after running on my 2008 stelvio for about 5-8min, a loss of power and unstable running was felt. "Just like that", while riding at 30mph... after i stopped, idle speed could not maintain, and the bike stopped. I realized the engine started to run only on one cylinder.
Was obviously very hard to start it again, but i got to start it and slowly drive back home.

Some details to help the diagnose:
- I use only quality 98octane gasoline.
- Yesterday ran just fine with the same fuel for about 40miles
- recently replaced spark plugs for new ones (the referred by manufacturer). To be sure that the fault had nothing to do with the new plugs, i installed the old ones, which are still ok, but the problem is still there.
- i realized the bike display crashed when the problem occured, so i could guess an eletronic issue might originated a faulty fuel injection when the engine got fully hot and the engine management reduced the fuel mixture.
- while driving back home, for one moment the full power came back and the two cilinders where available at higher speeds, for a minute or two. But again, the problem returned again when i slowed down.
- normally, when deccelarating, its been pretty common to ear exhaust explosions. Is it normal on other stelvios or should it mean that one fuel injector is getting faulty and leaking fuel impropperly?

What do you think? Any other ideas?

Thank you for your time. (Sorry for any bad grammar i may wrote)
Greetings from Portugal.
Pedro.

 

[canuck1969]

Sounds like you may have damaged the sparkplug boot or pulled the other end out of the coil. Are they the stock plug boots. They are notorious for getting damaged. Pull the boot on each plug and look for white burn marks on the boot all the way up to the wire. If you have them, for now wrap them in electrical tape but they will need to be changed.

Also make sure the other end of the plug wire is securely placed on the coil. They have a habit of coming loose and are not crimped on very tight. You can pull the small boot back on the coil plug and squeeze the crimp a little more to make sure it is secure. I then tie wrap the boot to the bike so it can't come off.

Hopefully those were the issues. Let us know.

 

[canuck1969]

Pedro, while you are in there, check the ground cable at the battery and also where they connect to the chassis and make sure they are tight. Would not cause it to run on one cylinder but would cause it to loose power mid ride.

As for the popping on decel (Exhaust explosions) that is somewhat normal on Stelvio running a stock map. They run more on the lean side. You can tighten up the exhaust gaskets also. It can help reduce the popping.

 

[not-fishing]

I was surprised at how much better my 07 Griso ran after just replacing the outside spark plug boots. They're cheap and easy to replace.

 

[Pedro Santana]

Hi.
@canuck1969
Thank you for your help. I've found the problem, the sparkplug boots (which are still the original stock boots) where conducting energy towards the Engine body. Found one white spot on the rubber, and while running, a few sparks could be seen. As reffered, i temporarly fixed it with electrical tape, and runs just fine. I'll surely replace the plug boots asap as you and "not-fishing" suggested. Thank you for all the tips!!

 

[canuck1969]

Pedro.....excellent news. Glad is was an easy one.

When you replace the boots replace them with NGK boots. If you do a search here you will find a lot of information on them. Attached is a link to a procedure on installing them created by one of the members here.

 

[Pedro Santana]

Very helpful indeed, that DIY procedure...! Thank you again!