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Stelvio misfiring/won’t take throttle.

macro1098

Just got it firing!
Joined
Jun 11, 2013
Messages
7
Location
Falkirk
I have a problem with my 2008 Stelvio 4V (never understood the different nomenclature of 4V/8V as they both have 4 valve heads). I have found the forum great for tech info and solutions over the years but I need some help on this one as I’m out of ideas.
Basically, the bike will start and idle ok, albeit a bit rough as if it’s only running on one pot, but it won’t take any throttle and just bogs down. If you snap the throttle open it will just stall. On the road it just feels like it’s running on one and will pull accordingly, occasionally firing on both and popping off unburnt fuel. So first assumption is plugs/ignition, however, the bike will actually start just as well on either cylinder with the other plug cap removed.
The fault first started showing a few months ago, and oddly only when the tank was almost empty. Fill the tank and all was ok. However after a long tour down to the alps it has progressed to be like this regardless of how much fuel. It has approx 24k miles on the clock.
Things I have tried;
New plugs/caps/HT leads
Checked fuel pump/filter
Checked air filter/airways clear
Checked valve clearances
Reset TPS and checked for sensible readings with throttle opening (with Centurion s/w from Todd)
Checked TB vacuum/balance
Swapped the exhaust can
No live faults on dashboard

So, I have a Guzzi dealer close and put the bike into the workshop today. The Guzzi mechanic has rechecked all of the above and also;
Run a full diagnostic
Checked cam timing
Checked flywheel timing pickup
Swapped a fuel tank c/w pump & filter from another Guzzi
Checked the stepper motor
Reflashed the ECU map to standard
Tested HT & injectors

No progress. He is out of ideas and we are both reluctant for him to keep fiddling away without a specific POA and charging me by the hour.

Has anyone experienced and similar problems or have any suggestions on what else we can try. Sadly the shop doesn’t have another Stelvio which they can swap bits off to eliminate potential faulty parts. I think he said the tank was off a Norge. All help would be welcome. I love the Stelvio, it’s a great bike when it runs well!!
 
Well, the 1st thing is to determine is it the spark, or the fuel, or compression. Then go after the one that is at fault. Has it been rollerized? Updated from flat tappets to roller tappets.
I have seen flats ground down at 10K mi on 2 different early Stelvio's.
4V= Early & 8V=Late usually means 1 or 2 lambda's in exhaust
 
You appear to have done all the basics but I'd add these thoughts.
Compression test
Is it different hot or cold
Lambda sensor
Did the valves need resetting when you checked them
Coils
Earth connections

Apart from that I have nothing I'm afraid

Good luck
 
Thanks for the comments guys, some more things to try.

It does look like I may have the flat tappet curse. I can’t say whether the bike has been rollerised but certainly the clearances have have always gone off quicker than I would have expected and on this occasion they were quite far out when I checked them. Definite question for the Guzzi dealer and try to push for the upgrade.

Could it really be that the wear has caused so much loss of valve lift to cause this running issue?
 
I don’t have the bike here to have a look but have just checked my service log and it mentions cam recall having been carried out in June 09. Would this be rollerisation or has there been more than one recall?
 
When 8V motor came out in 09 they had too flat of a tappet. Some had a square mark on them cause they didn't spin. All got changed, new & sold bikes.
 
So the dealer whipped one of the cam boxes off today and it has flat followers, which no surprise are badly worn, as are the cams, so that will have to get sorted first of all. Not overly hopeful about a warranty repair as MG UK are apparently very fussy about dealer service history, so that’s tomorrow’s battle!

Thanks for your help so far guys, at least the flat tappet problem has been identified before it got catastrophic.
 
So the dealer whipped one of the cam boxes off today and it has flat followers, which no surprise are badly worn, as are the cams, so that will have to get sorted first of all. Not overly hopeful about a warranty repair as MG UK are apparently very fussy about dealer service history, so that’s tomorrow’s battle!

Thanks for your help so far guys, at least the flat tappet problem has been identified before it got catastrophic.


With the amount of wear you seem to have be sure the dealer flushes the engine to get as much of the metal contamination out as possible.
 
So the good news is I managed to get a rollerisation kit under warranty, the bad news is it hasn’t fixed the problem!

The dealer has now pretty much exhausted all ideas by swapping parts off other Guzzi models (Breva & Norge) and the only thing he has not managed to eliminate is the ECU as he doesn’t have a Stelvio to pull one from. There seems to be some known issue with ECU’s being damaged if the bike is jump started from a car, which it has been previously? Anyway, when he connects the diagnostic tool, he can re-flash the box etc, but it doesn’t report what version of s/w is installed etc, just returns all 0’s, so it is suspect.

So unless anyone out there knows a friendly Stelvio owner in Central Scotland, I’m going to have to buy another ECU to try/eliminate.

There are a few available on eBay etc, but here’s the question. The specific model is a Marelli IAW 5AM 978477. Obviously the 5AM is widely used on Italian bikes so can I buy any 5AM, eg off a Ducati, and the dealer will then be able to reflash it to be compatible with the Stelvio or are there physical differences between the sub-models of 5AM meaning I would need to buy an ECU specifically from a Stelvio 4V? Clearly the latter will narrow down my purchase options.

Hope someone can help.
 
There are a few available on eBay etc, but here’s the question. The specific model is a Marelli IAW 5AM 978477. Obviously the 5AM is widely used on Italian bikes so can I buy any 5AM, eg off a Ducati, and the dealer will then be able to reflash it to be compatible with the Stelvio or are there physical differences between the sub-models of 5AM meaning I would need to buy an ECU specifically from a Stelvio 4V? Clearly the latter will narrow down my purchase options.

Hope someone can help.

I don't think you can. Some of the Ducatis use different pin outs. I suggest you contact Todd direct. He may be able to re-flash your ECU or may possibly have on in the shop. Use the contact function in the store tab. Shipping time will be your biggest delay, but it may very well be worth the waiting.
 
Hi..I know this is a old thread...but my 08 as had/ got same issues...went in a well known and respected guzzi dealer over here in UK..to have the cams up dated...hat off to guzzi for standing by a 11yr old guzzi and supplying the cams etc free of charge as done 19,000 miles but was getting noisey..machanic said none make it past 30,000 miles...think I got these free as from new no information had been past on to guzzi about my bike even though I have a full documented book on all servicing etc..anyway..cams fitted..bike running on 1 cylinder...faulty injector..another ordered from guzzi...still as issue..plus now Speedo will not registerer above 10mph...rode bike in to dealer was running fine...they now are 100% sure my ECU as failed as all wiring / plugs all been checked ..replaced from another bike...so why it decided to fail I do not know...shop as said all of my connections are clean in wiring loom with no corrosion..so I guess one of those things..they waiting on another dealer to send them a 08 ECU to try. 09s are different updated...hopefully diagnosis is correct and we will get sorted and I can get bike back..will up date when I know..cheers.
 
Bike back...was a failing in E.C.U..causing misfire on left cylinder and issues with dash and Speedo.. after new cams fitted.. just one of those things...got a brand new ECU from Poland £300 .. new old stock from when Guzzi sold aload of over stock off a few years ago...so a bargain.
 
Hi I know this is an old thread but my 09 stelvio has the same issue but only when cold. When warm it runs fine. I have done all the same checks as listed other than replacing the TPS which I am going to do just to tick off the list. Did you finally get the issue sorted? Any help welcome as i stuck. Thanks
 
My problem turned out to be gummed up injectors. Although the dealer tried swapping them out I‘m guessing the ECU had the mixture turned all the way up and he didn’t run the bike for long enough to let it respond the Lambda sensor. Anyway I diagnosed it by starting the bike on one cylinder with the other injector pulled out, it was clear that the fuel spray was wrong and most of the nozzles were blocked. I made a rig and flushed the injectors through with carb cleaner. The bike’s been running great since.
However, if you have a cold running problem, that may be a different issue, perhaps the stepper motor? You should be able to hear it whirr when you turn on the ignition. It’s a bitch to get to but perhaps you could simulate its operation by pulling the little rubber hoses off the TB’s and seeing if it runs clean on a cold start.
I can’t imagine the TPS being at fault as that would affect all running conditions, however, if you are going to replace it, don’t spend hundreds on the Guzzi branded part as exactly the same part No is used on lots of Fiats etc and I managed to get the identical thing for about £15. Google the part no.
 
Hi I know this is an old thread but my 09 stelvio has the same issue but only when cold. When warm it runs fine. I have done all the same checks as listed other than replacing the TPS which I am going to do just to tick off the list. Did you finally get the issue sorted? Any help welcome as i stuck. Thanks

Please, do not buy a new TPS. That is not your problem.

You need to send some spray carburetor cleaner down into your stepper motor via the intake hole inside and in the front of the airbox. You will need to do this a few times to fully clean out the oil gum.

This is well documented here via Search.

Most likely, too much oil was put into the motorcycle previously which blew excess oil into the air box and it got sucked into the stepper motor and gummed it up.

The stepper motor regulates air intake to maintain idle at cold engine temperatures. Once the bike reaches full operating temperature, the stepper no longer plays a role. Hence, your precise symptoms.

Once you get that oil gum out of the stepper motor, your problem will almost certainly disappear.
 
Last edited:
Please, do not buy a new TPS. That is not your problem.

You need to send some spray carburetor cleaner down into your stepper motor via the intake hole inside and in the front of the airbox. You will need to do this a few times to fully clean out the oil gum.

This is well documented here via Search.

Most likely, too much oil was put into the motorcycle previously which blew excess oil into the air box and it got sucked into the stepper motor and gummed it up.

The stepper motor regulates air intake to maintain idle at cold engine temperatures. Once the bike reaches full operating temperature, the stepper no longer plays a role. Hence, your precise symptoms.

Once you get that oil gum out of the stepper motor, your problem will almost certainly disappear.
Cheers for the reply’s
 
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