Mysterious V7 'stuttering' issue - can anyone help?

[jonmep]

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).
 

[Penderic]

Sounds like a vacuum forming in the fuel tank - pinched vent tube under the tank or the little one way valve is sticking.

Try removing the fuel cap when the problem occurs and see if the engine recovers.

[fotoguzzi]

I thought same/ next time it's doing it open the gas cap and see if letting in air solves it.. my lawnmower does that with full tank, no problem with less than 1/2 tank... is there relationship with how much gas you have in tank?

[sturgeon]

(Sorry, I can't help myself)

Has she tried it while not wearing a Triumph jacket?

And what was said above. Tank vacuum or dirty injector(s).

[sign216]

I does sound like a vacuum issue, but the dealers already checked that.  it's easy enough for you, just crack open the tank lid to release pressure, and see if the engine will run fine afterward.

How about a throttle position sensor (TPS) that's failing.  it can cause intermittent problems that are similar.  There's technique for cleaning them internally that buys you a few extra miles/yr or two, but replacing the TPS is the best bet.  You can test it with a voltmeter and some wires with needles, but I won't get into that here.

Also, since the bike a couple of years old, how about a failing fuel filter.  I don't mean a plugged one, I mean a half-plastic half metal one that's just beginning to split.  It's a long shot, but it comes to mind.

Joe

[jonmep]

Wow, thanks for fast responses guys!

Yup, tried popping the gas cap off - no change. No correlation with how much gas there is in the tank. The dealer suggested a vacuum issue too and looked around under the tank for pinched hoses but found nothing amiss. They checked the bike history and found that it had had the fuel pump and the one way valve thing replaced under warranty at some point. Maybe searching for the same problem?

I don't even know whether to look for a fuel issue or an electronic issue. If I had a spare V7 I'd switch a few parts one at a time to see if it fixes it: ECU, coil(s?), O2 sensor.... If it was still under warranty that's what a dealer could do I guess but it isn't so I'm a little nervous about what happens next. It could cost an arm and a leg to go off down a rabbit warren like that.

It's not 100% reproducible so it's super hard to pin down. It's done it on most longer rides but tends to resolve itself after a while. The video was shot when it was doing it badly and that was after about 2 hours on the highway. Took an hour break - still the same. Left it two days, works fine again! Argh!

[raul]

How many miles on the bike and have the plugs ever been changed?

[jonmep]

I does sound like a vacuum issue, but the dealers already checked that.  it's easy enough for you, just crack open the tank lid to release pressure, and see if the engine will run fine afterward.

How about a throttle position sensor (TPS) that's failing.  it can cause intermittent problems that are similar.  There's technique for cleaning them internally that buys you a few extra miles/yr or two, but replacing the TPS is the best bet.  You can test it with a voltmeter and some wires with needles, but I won't get into that here.

Also, since the bike a couple of years old, how about a failing fuel filter.  I don't mean a plugged one, I mean a half-plastic half metal one that's just beginning to split.  It's a long shot, but it comes to mind.

Joe

Interesting. The fact that it's intermittent troubles me - it makes it seem like an electronic issue (maybe my reasoning is faulty) so your failing TPS sounds plausible. I keep finding myself saying things like 'failing ECU' or 'failing sensor' - my reasoning being that something is getting gradually heated up and starts failing at some point. Leave it to cool down for a few hours and it's ok again. This most recent bad episode (in the video) was in hot weather although it was fine the day before (for the whole 300km day) and it was hotter.

The bike is back at the dealer at the moment for one last attempt to locate the issue. Maybe I'll call and suggest the faulty TPS to him and see what he says. If the bill starts getting to high I'll have to take the bike back and try to sort it out myself.

Thanks for the suggestions everyone.

[jonmep]

How many miles on the bike and have the plugs ever been changed?

29,000 km. Yes, we got the bike serviced as soon as we got it: TPS reset, TB Sync, valves, new plugs, new fluids, check for pinched pipes.

[jonmep]

If the valve and pump were changed, there's the possibility of the fuel line routed such that it either has a sag or loop, or it's lying near something that gets hot.  This can cause vapor locks.  Otherwise it sounds like the vacuum (tank suck) problem or maybe a bad/dirty crank position sensor.

Has the fuel finlter been changed?

Has the fuse/relay block gotten wet?

I once had a few days of bad running on a trip.  It started after a fill-up so I suspected it was gas.  I refilled at about a half-tank with no good results.  I was still convinced that it was bad gas so I drained and refilled the tank.  The problem improved but was not solved.  So I replaced the fuel filter on the assumption that the gas was so bad it blew chunks into it.  The problem went away.

I've also had intermittent running and dead-stick after plowing through horrendous rain and road water.  The side-of-the-road analysis showed the main ignition relay was full of water (oem relay) and the connctions in the socket were gummed up with green paste.  I swapped out the relay and blew the paste out with electromotive (CRC product) and went on my merry (wet) way.

Good suggestions - gives me some things to try and/or discuss with the dealer. Thanks!

[Chuck in Indiana]

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

[fotoguzzi]

  maybe a bad/dirty crank position sensor.
 

Cam sensor on your bike? how about the wire from it has a severe bend in it (right where it exits the block) and when hot shorts itself out?
something like that occurred on  V11 or spot1100's?

have you talked to Moto International?

[Vasco DG]

Phase sensors don't tend to fail intermittently. They either work or they don't.

First thing to establish I if it is spark or fuel related though. At the moment it sounds like spark.

Pete

[kevdog3019]

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

:+1

[jonmep]

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

Yeah I thought about that too. Thanks. 

Phase sensors don't tend to fail intermittently. They either work or they don't.

First thing to establish I if it is spark or fuel related though. At the moment it sounds like spark.

Pete

It started out just as an occasional hesitance when rolling on the throttle and I was sure it was a fuel issue. But since it did it really badly that day I'm more and more convinced that it's spark related.

All good suggestions. The challenge will be to tick off possible causes without spending a fortune. Also, it'll be hard to know when it's fixed given that some days it's been fine for hours! I'll report back with findings.
Thanks again everyone.

[jonmep]

Well the dealer said he couldn't find anything definitively wrong, just a few little tweaks like valves a little off, etc. Nothing that would cause the issue we have. He said that TPSs don't fail gradually, they just work or don't.

One thing to note that I think is very significant: When it's playing up like this it is still basically fine under hard acceleration, maybe with an initial hesitation. In other words, it won't idle or cruise at a constant speed but if you give it full throttle it accelerates normally. I feel like this should exclude some things from my enquiries, such as fuel filter and coil, and point to something reasonably specific... but I don't know what. I'm crossing my fingers that someone will suddenly recognize this collection of symptoms, like in an episode of House!

I'm going to pick the bike up at the weekend and take a look at a few of the things suggested above. Can't believe we picked up such a nightmare with a clean 2010 bike. My wife is sad :(
Anyway, lesson learned. Always buy from a dealer and get a warranty.

[Kev m]

Well, fwiw, a TPS could fit your description as it could have a problem at one throttle opening but not another.

I wonder if a coil could act that way too based on the difference in load between idle and WOT?

[Vasco DG]

A dud TPS will usually show up in the live data on any of the proprietary scan tools. Sometimes it needs the vibration of the running motor to be apparent. Does your dealer have PADS or NAVI? (PADS is easier.) Just plug the useless bit of shit in and data-log what the TPS is doing. If its the TPS it'll show up quick enough.

Quite often just reading the live data and twisting the throttle will show up dead spots though. The engine doesn't need to be running.

And no, they don't just work or not. They are a simple rheostat. They can fail at one point and still be perfect elsewhere. Your symptoms are atypical of TPS failure but that doesn't mean it isn't TPS. Log it.


Pete

[Chuck in Indiana]

I see Pete beat me to it. Never mind... although come to think of it, back in the days of the dinosaurs, I had TR software with graphing on a Palm Pilot, and it wouldn't show a glitch in the bad TPS on the Jack-All. There was a definite spot where it wouldn't run, though.

[Scott of the Sahara]

My friend had a bike with an intermittent problem. It would run rough when it was hot. He spent 2 days rebuilding tha carbs (6 of them) still no joy. Coils were bad. the Coil can't be that expensive...

[jonmep]

A dud TPS will usually show up in the live data on any of the proprietary scan tools. Sometimes it needs the vibration of the running motor to be apparent. Does your dealer have PADS or NAVI? (PADS is easier.) Just plug the useless bit of shit in and data-log what the TPS is doing. If its the TPS it'll show up quick enough.

Quite often just reading the live data and twisting the throttle will show up dead spots though. The engine doesn't need to be running.

And no, they don't just work or not. They are a simple rheostat. They can fail at one point and still be perfect elsewhere. Your symptoms are atypical of TPS failure but that doesn't mean it isn't TPS. Log it.


Pete

I'm not sure what system he was using but he mentioned that he had the newer/better system than the first dealer I took it to. He did the diagnostics and looked at the logs. The other thing is that he took the bike out for a 20km ride and it ran perfectly. I suspect he was working the bike a bit as that is normally what shows up issues... but not this issue; you need to sit at a constant speed for a bit. My wife reckons it's about 4k rpm.

You've made we wonder whether he tested the TPS through the entire range. I think he said he checked it at idle and 3k. Maybe there is a dead spot and the problem only becomes apparent when you've been riding at or about that dead spot for some time. That causes temporary knock on effects such as the idling problem. This would explain why the issue only becomes apparent after a while on the highway; when you're working the gears/throttle it doesn't seem to happen. Should be easy enough to check. Thanks. Fingers crossed.


 

[Kev m]

It is true that a dead spot usually shows up consistently, regardless of temperature.

But anything might be possible, i.e. it might be possible that it only shows up at that same spot AND a certain temperature.

I wouldn't expect the scan tool to show you anything if the symptom wasn't present. I mean, if it's not present, then whatever condition is causing shouldn't be either right?

So the problem becomes you have to either datalog it or be watching the scan tool reading WHILE the bike is doing it.

[rbm]

Phase sensor / cam sensor -  Do you guys mean the revolution sensor?

Talking BMWs for a second here.  If this were a BMW R-bike or K-bike, and these symptoms were described, I'd be examining the bike's crank position sensor.  BMW uses a Hall Effect Sensor (HES) with a toothed wheel to determine crank position and therefore timing.  The HES tends to go intermittent and exhibit these symptoms.  To verify, one test is to heat up the HES with a blow dryer; if it is weak, the symptoms will appear when the HES is warmed.

The MG Classic appears to use a variable reluctance sensor.  Cabling is shielded to ensure noise does not affect the signal.  Granted the sensor is probably passive and not active but, if the sensor is bad or the wiring bad, it still might not send a reliable signal to the ECU.  I'd verify the test procedure as described in the Service Station manual just to eliminate that component from suspicion (sounds like CSI, right?).

[Stormtruck2]

29,000 km. Yes, we got the bike serviced as soon as we got it: TPS reset, TB Sync, valves, new plugs, new fluids, check for pinched pipes.

Were the plug wires and caps replaced??

[Chuck in Indiana]

Phase sensor / cam sensor -  Do you guys mean the revolution sensor?

Talking BMWs for a second here.  If this were a BMW R-bike or K-bike, and these symptoms were described, I'd be examining the bike's crank position sensor.  BMW uses a Hall Effect Sensor (HES) with a toothed wheel to determine crank position and therefore timing.  The HES tends to go intermittent and exhibit these symptoms.  To verify, one test is to heat up the HES with a blow dryer; if it is weak, the symptoms will appear when the HES is warmed.

The MG Classic appears to use a variable reluctance sensor.  Cabling is shielded to ensure noise does not affect the signal.  Granted the sensor is probably passive and not active but, if the sensor is bad or the wiring bad, it still might not send a reliable signal to the ECU.  I'd verify the test procedure as described in the Service Station manual just to eliminate that component from suspicion (sounds like CSI, right?).

It certainly couldn't hurt to check the phase sensor. From memory (not a good thing at my age) about 600 ohms. Check to see that it doesn't have any swarf on the end, wiggle the wires around, etc.
This is *assuming* the V7 uses the same phase sensor that they've used for oh, 30 years or so.. ;D

[jonmep]

It certainly couldn't hurt to check the phase sensor. From memory (not a good thing at my age) about 600 ohms. Check to see that it doesn't have any swarf on the end, wiggle the wires around, etc.
This is *assuming* the V7 uses the same phase sensor that they've used for oh, 30 years or so.. ;D

I'll add that to the list of possibilities. Again, it sounds plausible. All these suggestions sound plausible... so it's a long list haha!

Were the plug wires and caps replaced??

No. The dealer mentioned that one of the leads seemed a bit loose and the rubber boot was torn - he sorted those two things out. He also said the TPS needed to be reset, idle was a little high, inlet valves a bit off, exhaust gaskets leaking, and plug gaps a bit too big. He's sorted that lot out and suggests we try it like that first before going any deeper into it. He's hoping that all these little things combined to cause the problem. Seems hopeful but we'll take it for a couple of rides to see.

He looked up the cost of a replacement TPS - $350, plus tax, installation and setting. Yikes! I'd want to be pretty sure that it's faulty before going that route. Is it possible to test it definitively? The dealer said he saw no diagnostic errors and as the bike felt fine to him on a 20km ride he feels that it's a bit of an expensive long shot.

[Stormtruck2]

It's my understanding that the plugs, wires, and caps are to be replaced every 6,000 miles. (9656 Kms)  NGK seem to be the best set up going right now for them.

[Xlratr]

Are the plugs the correct type?
As the problem is intermittent, this probably isn't the problem, but worth checking just to cross it off the list. A friend of mine once had a poor running bike after a "service" and at the end of the day we discovered they'd put the wrong plugs in.


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[guzziks]

Injector problem, like dirt or corrosion, where when at full throttle, they open enough or long enough that it fuels okay, but at idle or constant load not enough gas?  especially when hot and it is leaning out anyway?

Or maybe the coils on the injectors are faulty.

just another off the wall idea if it seems related to a fuel issue.

[jonmep]

Yup, correct plugs, although they were mismatched when I first had it serviced. Problem existed before and after that.

So far the best fit is an intermittently failing TPS with a particularly obvious problem around 4500 RPM, although when it's playing up it also idles erratically. Some days it's fine and others it's not so maybe there is a humidity correlation (there isn't a temperature correlation), or perhaps it's just certain vibrations that cause it to act up. Yesterday we rode ~80km and it was fine although when I held the engine (in neutral) at 4500RPM I could hear a slight 'burble' - nothing that you could feel when riding but it sounded different there, and that is where it misbehaves most when the problem is manifesting.

I have heard that there is a Harley TPS that is almost identical and much cheaper but before I dig too deeply into that I'd like to figure out how to test the TPS with a multi-meter so I can test it when it's playing up rather than taking it to the dealer when, of course, it always runs fine! Would an intermittent dead spot in the TPS show/log anything in the diagnostics? Would the ECU know that something was amiss or just take the incorrect TPS output at face value?

If anyone can give me any tips on testing this myself it would be greatly appreciated. I'm hoping there is a way to do that won't require resetting the TPS as the dealer is 100km away.

Thanks for all the input everyone.

Jon