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Power issue?

1942 Views 9 Replies 4 Participants Last post by  Joshuwaa
Hey all

Weird issue popped up in the last couple of days on my 2010 ABS Wee. I'd appreciate any and all ideas of things I can look into!

I did a month long trip in Europe a month or so ago, and have ridden a few short rides since then and noticed no issues. Jumped on yesterday and the following happened.

  1. Weird power drop as I pulled out of the drive, didn't think much of it.
  2. Pulled around the next corner and got some weird power drop and knocking. Revd up and it picked up just fine.
  3. did a U-turn back to my house and it just struggled for power at below 3k rpm, just dropping and knocking
  4. leaving it to idle and it almost stalled out, dropping to about 900rpm before picking up to 1200 and dropping randomly again.
I suspected spark plugs as they're overdue a change but have been working fine, so I swapped those out. That seemed to give some improvement, but once the engine warmed up (3 bars on the temp), it started wildly fluctuating again. When sitting at idle it's sort of wobbling in RPM. It doesn't stall but definitely isn't healthy either.

I've put this bike through the absolute ringer on a RTW trip so I'm not at all surprised something is wrong 馃槄 I'm just surprised it came up out of nowhere and the nature of it. I've had a small issue with the fuel pump previously, but that was over 10k miles and 4 years ago. but that's where my main suspicions lie now. Maybe the injectors are clogged but I would have expected a slow degradation, not all or nothing, and I don't think it would jump up and down like that, just have less throughput?

I also suspected the throttle valves getting stuck, but when it's idling I don't belive the ECU really controls them much does it? I assume they'd have an "idle position" and just stay there?

It doesn't appear to be electronics related as it's started up multiple times yesterday as I was trying things and had no issues doing it.

Any ideas would be appreciated! I've included a video of it idling, but the wobble in RPM is hard to hear really.

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Put the bike in dealer mode and check the TPS
Also do a fuel flow test, it's not hard and can tell you a lot
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TPS. Diagnosing is often inconclusive. Typically happens more when fully warmed up. Often at a particular throttle position. Symptoms vary. Mine would act like an old, carb'ed bike about to go on reserve & wouldn't maintain speed. Let it cool off for awhile & all normal: 'till the next time.
TPS is a good shout! I forgot it was sat out in the rain a couple of days last week, that could be the cause if it is the TPS. would just a dealer mode check reveal much? It looks like a bugger to remove and test properly with the alignment checks and torx screws :oops:
There is a rough and ready TPS test.

It is not a grantee answer but it may help you decide.

Fully open and close the throttle about 10 times with the ignition off then test ride to see if there is a difference.

This wipes over the contacts with no power running through it, it can clean the contacts enough to make a difference for a very short time, if you get a difference that points to it being the likely cause.
Thanks all! After a quick TPS dealer mode check (at normal engine temp) I think this is the culprit. It's sitting at the low position at idling and not moving to the middle until around 1800rpm, then not to high until over 4000rpm. There's a weird fluctuating behaviour too, sitting with the throttle as still as I can possibly keep it, there are times when it will swing over a 400rpm range up and down. This doesn't seem healthy and not something I've ever noticed before. My theory is the TPS is just ** and needs replacing. Unless anyone has any other theories that might explain both? As far as I'm aware, there's nothing else that would cause the TPS check to report LOW at idle, other than the TPS being out of adjustment? (except maybe ECU buggered too).

here's a little vid of me trying various throttle positions. If I'm not gradually climbing or dropping the revs, I'm holding it stock still, so you can get an idea of the scale of fluctuation at different positions. It seems to be worse at higher RPMs, which tracks if the TPS is out by a percentage, it would scale?

EDIT: Also, since there's also the Secondary TPS, if I do replace it, do I need to replace that too? what does it even do, if the primary is broken does it just take over, could that be why it's now out of alignment?

EDIT2.0: I managed to find some Torx alan keys and adjusted the TPS slightly. it's now in the middle at idle and at the top about 1700rpm ish. It is far better now, idling more reliably and I took it out for a ride, much better throttle response and not bogging as much. There's still a big issue though. It just occasionally bogs hard and struggles to pick up, seems to be when it's under load. Pulling off or in 3rd at lower revs, just feels like it's really struggling and ends up knocking and firing very oddly.

The RPM fluctuation hasn't diminished at all either, some very wild swings when holding the throttle perfectly steady. This could be what causes the bogging? If I'm giving it throttle but it's a "down" swing so it doesn't get fuel and just bogs hard?

I think all the adjustments has done has make it run richer(?) and masked whatever other problem is there. The TPS clearly wasn't doing well but it's adjusted to richer than spec and still struggling with power. 馃 it's at the mechanic tomorrow for a tyre change anyway, can anyone think of anything I could get them to check while it's there? I'm not a fan of mechanics doing exploratory work, esp. on an older and abused bike, there's all sorts wrong that I know full well about that they'll get distracted by. But they are experts so if I can direct them to check some things I'm more than happy with that!
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Do the fuel flow test before you go.

A blocked high pressure filter can cause erratic fuel pressure & flow
That's a good point, I did one this morning (leaving for the mechanic in 10 minutes). The flow was OK, it was about 300ml after 3 ignition sequences, taking into account how much I spilled on my hand trying to catch it without a length of hose 馃槄. There was no obvious contaminants or gunk but it was pretty cloudy, I'm not sure if that's normal for what I filled up with since I rarely see it in containers :D it doesn't look right to me though. It was left sat for a LONG time previously, just over a year I think, but there was very little fuel in there and I topped up full with fresh and have ran it for about 5000 miles since then so I assumed that would have burned through by now, maybe not? I think I'll ask them to drain the tank fully and swill it out a bit, just to be safe, not a big job when you're already at a mechanic.

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So, update after the mechanic! We had a good natter about what else it could be (he didn't have good fuel to hand). He drained a lot of the tank for me and I filled up to full as I left. I shook the tank around a lot to get it mixed and set off on a much better bike! Power is back, less bogging and no misfiring! Seems it was just some shitty fuel all along.

I'm still not sure why, I filled it about 50 days ago from a motorway service station, ran it hard for 100 miles since then, then have done multiple little trips in the last month with no issues. maybe the last 2 weeks sitting still let the crap settle to the bottom or something. Maybe there's a leak in the filler cap and some water got in? who knows. at least I know what to look out for now.

Thanks all for the help! if there's any suggestions on cleaning up the tank I'd appreciate it!
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