Very intermittant miss or surge

[bicyclenut]

Have a 2010 R1200RT purchased used with about 52K on the clock and now about 14 months later it has just over 64K. With colder weather in Chicago it was not ridden for 3-4 weeks with our Halloween freeze and when I took it out I noticed what I would call a very intermittent miss, possible surge under load or at times when just cruising along. It is usually just a quick little blip and can happen miles apart on highway or sometimes when accelerating. I haven’t ridden too much lately due to weather, but did ride last 2 weekends and was hoping I was just imagining it or maybe it would clear up with a new tank of fuel. What I did notice the last 2 times I fueled up is my gas mileage dropped from an average of 41-43MPG to 36MPG last 2 fuel stops. I have been staying in 4th gear a bit more on highway to experiment a bit but seems like a pretty good drop. I also noted a couple times there has been a slight and intermittent backfire on hard acceleration.

Based upon the dealer I purchased from, the spark plugs were replaced at 47K and valves were checked at 52K when oil was changed before I purchased. Not sue when throttle bodies were synced, so I had planed to do this over winter as well as take a look at plugs.  Based on my reading, it seems like problem could be related to a bad stick coil but seems no easy way to test besides replace coils and recommendation is to replace all 4 at the same time.

In addition, I have always run premium fuel, 90% of time from top tier brands and added some Techron injector cleaner every couple of tanks.  Of note, when stopping for fuel a couple weeks before this all started, the bike fell over on crash bar when kickstand was not fully locked and I was probably in a hurry - no damage besides some marks on my highway peg on that side and my pride.

I preparing to just take a chance with stick coils but checking if any other ideas before I throw parts at it as I’m used to diagnosing problems with cars and not just bolting on parts without solid data or testing failures point to a fix.

[David.]

Based on my reading, it seems like problem could be related to a bad stick coil but seems no easy way to test.

Have seen a couple of videos & posts on other forums where, whilst the bike is running at idle, the LT lead on each coil stick is disconnected in turn.

The theory seems to be, if disconnecting the LT lead/coil doesn't make any difference to the running of the bike, that particular coil is suspect.

2004 BMW R1150GS Ignition Stick Coils, https://www.youtube.com/watch?v=hMJWr_BdNO8

[heathy65]

I had exactly he same problem on an 850 some years ago. turned out to be a fuel management issue. The mechanic who diagnosed it said it could have been one of six sensors or the fuel management computer (sensors around £100 each, computer around £1000).  Only way of fixing the problem was to start changing parts. Could have struck lucky on the first sensor changed or could have ended up changing the lot. On his advice I traded the bike in for something else.  That said it was still on the road some three years later.  Good luck resolving the problem.

[David.]

Intermittent faults are probably the most difficult to diagnose. Earlier this year, on a 2012 TC, had the ECU re-flashed by Hilltop Motorcycles. Prior to making any changes, Hilltop plug in their diagnostic equipment to check for any pre-existing faults. Unbeknown to me, I was told that there was a slight misfire on the RHS cylinder, "might have a spark plug off". This was identified by observing the knock sensor voltage which was fluctuating, whilst the LHS was fairly stable. It was suggested that the spark plugs were changed, now done as part of my servicing before tucking the bike away for winter.

As I couldn't feel the misfire in the first place, it's unlikely I'll feel any difference next year. Perhaps the key thing is how clever Hilltop and their diagnosis equipment are.

Just a thought, it may be worth having the bike checked with a diagnostic tester before throwing money at it.