Mysterious V7 'stuttering' issue - can anyone help?

[Tom]

Crank position sensor.  Clean the garbage off of it.  Clean off gaskets and reinstall the same way.

[Xlratr]

Can you establish if it's misfiring on both cylinders? Listening to the video, it sounds like maybe just one.


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[jonmep]

Can you establish if it's misfiring on both cylinders? Listening to the video, it sounds like maybe just one.

That was my initial feeling too but it's hard to say. Not sure how I could know for sure.

[Xlratr]

That was my initial feeling too but it's hard to say. Not sure how I could know for sure.

In the old days you could just pull one of the plug leads off and see if it made a difference. You're not really supposed to do that with the modern ignition systems though.
Try and get close and just listen. You might me able to hear if one side sounds different.

If it is missing on one side it could be one of the coils, or the spark plug cap.

Here is something I found on another site that sounds a bit like your problem:

"the plug caps are a bit fragile on this bike. they are easily broken between the the brass connecting tube and the resister. they are very hard to get off the plug and bending them around to get them off will break them. They will give all kinds of misfiring issues. I had one break and the bike wouldn't run on one cylinder below 4000 rpm".

Might be worth getting new caps again? You should be careful pulling them off. I'm not familiar with the small block and how easy it is to get a grip on the plug cap, but on the Stelvio a good tip is to slide a cable tie under the lead and make a loop to pull it off without damaging it.

If you are still suspecting the TPS, you can try checking that with the Guzzidiag Software. It's free (you can donate!), and even with the engine off you can see if the TPS is showing a progressive and smooth opening value. There is a nice thread on here on how to use the software. You do need to buy a couple of cables to do that though. 

[pauldaytona]

cam sensor can do this when hot. But can be checked when it has happend, engine should still be running, there are a few values for the tooth counter in the diagnostics, be it the dealer PADS or the free Guzzidiag. The counter should be at zero. Each failed read raises the number.

[guzziks]

one way to check for one cylinder running is to pur your hand near the exhaust pipe near the head.  the one not running wont be hot.  I do this all the time for my 91 ducati and my jd tractor.  But they are easy to tell cause the one that is not running/intermittant does it for quite a while after startup.

[rbm]

Or use an infrared thermometer.  Much safer.

[neverquit]

Back in the old days we used to cup our hands and hold them a couple inches or so behind the exhausts with the engine running.  We were looking for even pressure from the puffs of exhaust and afterwards we would check our hands for oil, soot or unburned fuel.  With the old British twins this often provided useful information.  It's not very accurate but it will certainly tell you if one or both cylinders are cutting out.

[Chuck in Indiana]

phase sensor

Crank position sensor.  Clean the garbage off of it.  Clean off gaskets and reinstall the same way.

cam sensor can do this when hot. But can be checked when it has happend, engine should still be running, there are a few values for the tooth counter in the diagnostics, be it the dealer PADS or the free Guzzidiag. The counter should be at zero. Each failed read raises the number.

These are all the same thing, and IMHO the next thing you should be checking.
The TPS on the V7 isn't the same as the Harley as far as I know.

[Xlratr]

Still think it's important to verify if it's misfiring on one or two cylinders first. That might give you more clues. For example:


If it's misfiring on one cylinder, I would assume it's not a phase/position sensor thing as that should impact both sides. (Anybody?)

If it's misfiring on the cylinder WITHOUT the TPS equipped throttle body, then I would think it's not a faulty TPS (as far as I know, the TPS regulates fuel, i.e. to the other cylinder, but has no influence on spark. Feel free to correct me anybody).

If it's misfiring on the cylinder WITH the TPS throttle body, well then you can't rule out the TPS :-(

If it's missing on both cylinders, then it's probably at least not leads / coils / plugs.


I know nothing about small blocks so somebody contradict me if that's nonsense :-). It would just be my process of elimination.


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[John A]

My bet is on a faulty electrical connection. Probly dirty connection or unseated wire in the affected system. Ignition and kill switches as well as side stand switch. Finding if it is only one cylinder or two will narrow it down. Look especially at the connections to the coils, injectors. May take sometime with a bright flashlight. Intermittent problems are especially troublesome but can be found and fixed

[sonicboom]

I'm a n00b on this forum so hello all! Me and my wife have a few bikes but mostly vintage stuff. She recently bought a 2010 V7 Classic with a view to using it for some longer trips on the west coast - we're in Vancouver BC and are planning a few rides around BC, WA, OR and CA.

BUT... the V7 has an intermittent problem that is rendering it unusable for our trips. She is pretty sad about it :(

Ok here's the issue:
Sometimes after 20-30 minutes it starts to 'miss' and stutter; some days it seems to be ok, it's about 50:50. When it starts doing this it will often not idle. The revs will hesitate, almost feels like it's choking, before picking up. When it gets really bad it will not hold constant revs and keeps stuttering. Sometimes a 15 minute rest will resolve it temporarily, other times it takes an overnight break to return to normal. When it's not doing this it seems to run great and it seems to be ok under hard acceleration which suggests that it's not fuel pump/filter. I managed to snag a video - the issue is easiest to hear rather than see. Note that she is trying to hold it at a constant rpm but the engine keeps stuttering and when she closes the throttle it dies:
http://youtu.be/UAjRoslZ9gA

Taken it to two dealers so far but they don't know what is causing it. They've looked for vacuum issues, serviced it, checked for error codes, changed the plugs, taken the exhausts on and off... nothing. At this rate we'd have been better off buying brand new (which we can't really afford).
 

Sir, you have already been told how to fix this.

I've seen this before on other bikes and each and every time it was nothing more then a coil going bad.

REPLACE THE COIL, they don't cost that much and that is almost always what will cause this issue. Sounds like all the basic stuff was covered already. Plugs, wires, electrical contacts, etc.

If you end up with an extra coil that is a good trouble shooting tool to own with any bike or nice to have with you on long trips.

[jonmep]

I back probed the TPS and it looks like it's working correctly, but the bike has been behaving nicely for the past week so that's not conclusive. I'll try to catch it happening if I can.

I cleaned the cam sensor but it was totally clean anyway.

It hasn't been playing up since we got it back from the dealer and we've put in 3 decent rides of over 100km each so maybe something he changed was the cause, it seems unlikely but until it starts doing it again it's impossible to debug further. Once/if it starts again we'll replace the HT leads then, if that doesn't fix it, the coils.

Off on a two week road trip on the bike in about a month so we need to resolve it one way or another

Thanks for all the help and suggestions. If I work through them all we'll fix the problem for sure!

[jonmep]

Just in case anyone reads through this trying to debug a similar issue I'll add an update:
Rode about 800km this past weekend with zero issues. It appears that the problem has gone. There was no single 'smoking gun' so I'm a little concerned that it will reappear at some point but until it does we have to assume it's resolved. Presumably one or all of the things the dealer addressed were causing the issue or maybe it's caused by something that has been absent since then (very specific atmospheric conditions?). The only I have done since last update was replaced the exhaust gaskets as there was an audible leak on one side. Fingers crossed!

[Kev m]

Thanks for the update...fingers crossed.

[NGC]

Hi, I just bought a 2013 V7 Special privately in January this year and I have exactly the same problem I think. After about a half hour at fairly constant throttle 45/50mph in 5th it feels as if there is fuel starvation.. Accelerating and varying the throttle seems to clear it - doe this sound familiar to your experience and if so has your V7 done it since 2014?

[davedude]

Do these SBs have the half plastic fuel filter? When they start to swell and separate, you get "that". Replace with an all metal BMW ff from MPH cycles or x ref NAPA p/n. You could probably take the old one to NAPA and do a visual comparison. I had that problem on an '07 Nev.

[Kiwi_Roy]

Are there any other symptoms you aren't telling us about, flickering dash symbols or lights?
The video doesn't work for me.

Use this drawing.
http://www.thisoldtractor.com/guzzi007/schematics/2008_V7_Classic.gif

Several mentioned the RPM sensor, find the connector (1) and measure the resistance, post it here. Carry the multimeter and next time it plays up measure it again the reading shouldn't change.

When you measure the Ohms switch the meter leads, it should read exactly the same.

Pete mentioned in reply #17 using a scan tool, failing that;
Measure the TPS (15) Voltage to chassis by poking a sewing pin through the wire, make a semi permanent arrangement with wires to a convenient spot. The Voltage should vary smoothly from a few hundred mV to just a bit less than 5 Volts as you open the throttle. I think the wire you need to measure goes to 11 on the ECU plug but it' wouldn't surprise me if it goes to 1
(you can't really check it by resistance alone as it's not a simple potentiometer)

From the ECU connector you can measure the sensors, the left and right side should measure the same, injectors ~ 17 Ohms, coil primaries ~ 1-2 Ohms
The two engine temperatures will be the same when the bike is cold ~3.5K Ohms but the oil temperature will be much lower than air temperature if the bike has been running.
measure from each plug cap to chassis, probably in the order of 8K ohms, whatever it is within 5% of each other.

Over the years the side-stand switch (13) has proven to be unreliable, 50% of older bikes have it removed or shorted out, does it cause the bike to stop when deployed?

I sent you a PM

[rbm]

Do these SBs have the half plastic fuel filter? When they start to swell and separate, you get "that". Replace with an all metal BMW ff from MPH cycles or x ref NAPA p/n. You could probably take the old one to NAPA and do a visual comparison. I had that problem on an '07 Nev.

List of compatible fuel filters:
Deutsch FF424
Fram G3802 (for Ford Mustang 4.6L V6)
Napa Gold 3032
Triumph T1240850
AC GF61
BMW 16 14 325 859
Fleetguard FF149
Knecht Mahle KL145
Motorcraft FG-2
Perolator F20011
Wix 33032

[LaMojo]

A coil that is on it's way out will first start to act up when it's hot. Just a thought.

:1:

[Kev m]

NGC BE CAREFUL reading threads about V7C or earlier 2TB smallblocks. The ECU setup is dramatically different and little from the 2TB EFI system applies to the 1TB system.

Are there any other symptoms you aren't telling us about, flickering dash symbols or lights?
The video doesn't work for me.

Use this drawing.
http://www.thisoldtractor.com/guzzi007/schematics/2008_V7_Classic.gif

Several mentioned the RPM sensor, find the connector (1) and measure the resistance, post it here. Carry the multimeter and next time it plays up measure it again the reading shouldn't change.

When you measure the Ohms switch the meter leads, it should read exactly the same.

Pete mentioned in reply #17 using a scan tool, failing that;
Measure the TPS (15) Voltage to chassis by poking a sewing pin through the wire, make a semi permanent arrangement with wires to a convenient spot. The Voltage should vary smoothly from a few hundred mV to just a bit less than 5 Volts as you open the throttle. I think the wire you need to measure goes to 11 on the ECU plug but it' wouldn't surprise me if it goes to 1
(you can't really check it by resistance alone as it's not a simple potentiometer)

From the ECU connector you can measure the sensors, the left and right side should measure the same, injectors ~ 17 Ohms, coil primaries ~ 1-2 Ohms
The two engine temperatures will be the same when the bike is cold ~3.5K Ohms but the oil temperature will be much lower than air temperature if the bike has been running.
measure from each plug cap to chassis, probably in the order of 8K ohms, whatever it is within 5% of each other.

Over the years the side-stand switch (13) has proven to be unreliable, 50% of older bikes have it removed or shorted out, does it cause the bike to stop when deployed?

I sent you a PM

Who are you replying to? The two year old OP or our new friend with the 2013 1TB smallblock the uses a non adjustable TPS integrated into the ECM/Throttle Body assembly?

[Kiwi_Roy]

NGC BE CAREFUL reading threads about V7C or earlier 2TB smallblocks. The ECU setup is dramatically different and little from the 2TB EFI system applies to the 1TB system.

Who are you replying to? The two year old OP or our new friend with the 2013 1TB smallblock the uses a non adjustable TPS integrated into the ECM/Throttle Body assembly?

Damm, I hate it when that happens LOL
The threads should disappear after 1 month of inactivity.

[old as dirt 2]

funny you guys brought this up. today I went for a spring ride up to the Dragon. had lunch at Tapoco lodge, (highly recommended BTW). and left out for the skyway. I got a red malfunction light then the bike started to miss like it went into limp mode. after a mile the light went away and all was fine. It did this again after about 5 miles.
So I stopped along side the road and couldn't see anything obvious, I pulled the plugs had spark on both. started it back up and it was still missing.  then I looked down at the right side HT wire and plug and I could see the arcing from the HT wire to the cyl.  a bit of black tape wrapped and all my issues went away.