cutting out problem solver required!

[ahg]

The bike
1200 GS 2009 (single cam)
Engine mods ….carried out over 28000 miles ago
No cat, no sensors in headers, after market silencer, K&N filter, PC5 with custom mapping.

Problem
Intermittent erratic takeover (max range from base plus 500 to as low as a stall)
Intermittent instant dying when clutch pulled in. Only happens after above has kicked in previously

Background
Not engine temperature related
Not wet/dry related
Not how long been running related
Cannot control bringing on or remove problem by operating/fiddling with anything
It can start shortly after firing up or not at all
On only one occasion tick over went to 2000 rpm on start-up and reverted to normal after about 5 minutes of running
It can happen several times a day for several times or not for weeks
Happens on old and new plugs
Nothing shows on dealer diagnostics and of course it never happens when at dealers
Has not always happened but has done for over 3 years and seems to be getting more frequent
Cut out only happens at low revs when clutch pulled in
Bike performs very well even when tick over issue at lower revs is apparent
Fuel consumption is good (44-48mpg) and has not varied much over the years
Plug chop and exhaust show good colour

Help
Has anyone else had this and cured it?

 

[Bendy toy]

If it's on the original coils and they smell "hot electrical" you probably need new primary coils BMW diagnostics does not show a failing coil.
Also check the throttle cables are all 100% and the TPS is in good condition.
If it is the coils buy a pair because they will fail at similar age/ miles.

 

[Magwych]

Yep, had that when I had Power Commander III. I was not impressed with the quality of the connectors, nor the lack of sealing on the connectors. Took it off and erratic problems went away.

 

[Magwych]

Oh and a dodgy lambda does the same too.

 

[Pukmeister]

Yep, had that when I had Power Commander III. I was not impressed with the quality of the connectors, nor the lack of sealing on the connectors. Took it off and erratic problems went away.

Same thing with a mates GSA whilst touring in heavy rain, unplugging his PC3 solved it instantly.

 

[bobtail]

Had a Similar problem on a GSA I have with a Pcv fitted , water getting in to connectors simple fix separate fittings put some electrical silicone grease to the fittings , replace , no trouble since , poor quality connectors on Pcv

 

[Bendy toy]

My first failing coil messed up a lambda. Misfiring puts unburnt fuel down the exhaust. As not all the oxygen gets used the ECU adds more fuel and that clogs everything up.

Check exhaust header temperatures.
Swap coils left/right and see if the problem moves.

 

[ahg]

Thanks for the suggestions guys. Appreciate the responses which I have considered with my thoughts below. If you think I am off track then please say.

I do not believe it is damp related as the problem can occur after the bike has been running for weeks in no rain (USA). The connections are also all acf50 treated

If the coils were failing would that not effect the performance too. Performance and MPG is good.

The lambda's are not connected due to the PC5.

TPS. Any ideas how I could test this? Can they fail intermittently over several years? A swap (if I could find one to try) would be a two or three day affair as cannot be sure the fault will show its self in less running than that. If considered opinion is TPS are there better outlets than a dealer to source from?

All suggestions appreciated

 

[Bendy toy]

Mine had both coils failing intermittently for months. It would stall suddenly for no reason then be fine fuel consumption was ok until one coil finally failed completely. The old black body type is less reliable than the replacements.

The clue was that both coils smelled burnt electrical though they still appeared to work properly. I suspect the secondaries can mop up minor missfires from the main coils, but they cant mask the problem at low revs. When the mains do fully fail you will get the bad fuel consumption and sooted up lambda sensor.

My suggestion is see if the coils smell burnt. If they seem bulged, rusty or smelly, try to borrow a known good pair because new coils are about £80 each.

 

[Pukmeister]

Do you have access to a GS911 diagnostic tool? The TPS output values should be measurable in real time as a variable value. If this value changes suddenly between its range of maximum and minimum values when rotating the throttle you have a fault with it. Its output should be pretty linear IIRC.

As Bendy states, coils can break down under load and give intermittent running faults, as can spark plugs. I have known one instance where a spark plug fault was only found during a late evening when you could see the sparking across the outer insulator (not visible in plain daylight, car engine).

It could be worth just changing the spark plugs first if they haven't been done for a while as a cheap and simple first step.

 

[ahg]

Thanks for the further advice guys. New plugs tried a few weeks ago. I have booked the bike in for a rolling road diagnostic and hope that this will reveal all! The dealers diagnostic showed no faults.
I don't want to put the bike away in October/ Nov and have to start messing about next spring when I should be riding it.
Time will tell
Cheers

 

[Pukmeister]

Reading your original post again, I'm leaning towards a BMS-K problem with idle speed sensing and stepper motor control which needs a dealer diagnostic to find.

I'd be tempted to return to standard spec then see if the fault reoccurs.


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