ER6 Low RPM trouble

[Scrap]

Hi all. I have a 2009 ER6 with 60k on it, normally used a few days a week and earlier this week the bike suddenly started playing up.

At low or idle RPM, the engine is intermittently dropping revs, like a on/off switch - one second it's ok, next second it's dropping revs; it's either dropping revs or it's ok - there's no middle occurrence where RPMs drop slightly. Pulling out of a T junction for example, the bike can stall because RPMs can drop at the same time I let the clutch out, so I have to give it a load of throttle and keep the clutch in for longer.

At over 2.5k-ish RPM the problem goes away. No dropped revs, no skips. I have noticed that when the revs drop, the exhaust can pop, and I can smell unburnt fuel.

On idle, the revs can intermittently drop to about 700 rpm. Revs can quickly bounce between normal 1.1k and 700 so sounds like a rough idle. With a little bit of throttle, it will bounce between, say 1.8k and 800k - it will 'sit' at either and not in between.

It did this on my 20 min journey to work and also the way back, it wasn't a particularly hot day - I've had the bike out doing the same journey when it has been much hotter.

I suspected the throttle position sensor might be bad. So I did some back-probe diagnosis using an oscilloscope on the connector at the TPS and the ECU:

- 0V and 5V are good and stable, when the key is on engine off and engine on.
- When the key is on engine off and engine on, the idle position is dead on 1.0V as per the spec in the Haynes manual, and the sweep is nice and smooth up to 4.4V with the throttle fully open, again exactly as per spec.
- There is no sign of the signal or voltages dropping, the curves are smooth and consistent.
- The readings are the same at the TPS and ECU connectors.
- Connectors at both the TPS and ECU look good, no sign of debris or corrosion.


And of course, the problem has now disappeared... Maybe a crap connection which I've wiggled when diagnosing and inadvertently made better.

So while I wait for the symptoms to come back and do my diagnosis again, what else should I look for? I've ordered a TPS connector adapter so I can probe more easily next time.

[stinkwheel]

Battery holding a good voltage?

Maybe try a new set of plugs in it, could be dropping a cylinder?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.