Throttle surge - but only when cold

Beemerman59

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Bikes an '08 GSA. Strange issue yesterday - started bike up and rode 15 miles to refuel. Then a 50 mile motorway run to my parents - all good so far. But when I restarted the bike after a couple of hours, the throttle was surging independently of the twist grip. The idle was high and the revs would go up and down between 2K and 4K. Had an interesting time getting to the local hospital (not for me - just visiting) having to feather the throttle using the clutch and rear brake. After leaving the hospital the engine was still cold and the surging was continuing however, once the bike had got to normal temps the problem went away and was running as per normal.

My first thought is the splitter box and a sticking cable but can't understand why it would disappear when warm. I haven't had the tank off for a while and the cables are routed OK at the throttle bodies. I haven't been inside the splitter box yet - should there be a need to lubricate at all?
 
It sounds like you might have an air leak between throttle body and cylinder head. Also do the throttle position sensor reset.

This might help
BMW TPS Reset TPS reset routine:
1) Disconnect battery for about 30 seconds then reconnect (causes ECU to lose it's memory of Throttle Position Sensor).
2) Turn ignition to on but DO NOT start the engine.
3) Slowly wind the throttle fully open to fully shut, repeat this three times.
4) Turn off ignition. (ECU now stores TPS position data in memory).
5) Wait 5 seconds.
6) Turn on ignition again and start bike. Before doing this, I would check that the wiring to the TPS itself hasn't been kicked or disturbed, its the electrical unit on the air intake in front of your Left foot.

Robbed unashamedly from here - http://www.ukgser.com/forums/showthread.php/239162-TPS-Reset

Coils are another possibility. Generally they fail when hot but you can never tell. A misfire will mess up the engine fuelling so anything can happen as the ECU tries to correct itself.
 
Sounds like mine when had the PCV on it.
Believe it happened when moisture got into the TPS connectors. Happened in heavy rain or if I'd washed it.
 


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