I'm wondering if I'm experiencing the initial indications of a looming issue. During the cooler Northwest Florida winter months (low to mid 40F in the morning), upon initial startup (cold engine) my 2000 LT would immediately rev to approximately 1400 RPM and then settle to approximately 1200 RPM after a few seconds. Everything was good.
Now that the temperatures are warmer in the morning (mid 70F), the LT on initial startup (cold engine) will rev to approximately 800 RPM and not idle well until I give it a short twist of the throttle. Additionally, the battery warning light illuminates (the battery stays on a Battery Tender overnight). After I give the engine a shot of fuel from the throttle the RPM stabilizes at approximately 1200 RPM, the battery warning light extinguishes, and everything is good.
The low 800 RPM and battery warning light indications only occur during cold engine starts. I can make multiple engine starts after the engine has warmed without experiencing the indications.
Is there something I should inspect or I am making a mountain out of a mole hill?
Rob, 2000 LT
Charging / battery warning is a consequence of too low idling, but no cause for alarm as it is normal that it will be a bit low as alternator / charging system was designed for a normal idling of 900 to 1050 RPM. When the low idling problem is fixed, you should not see this warning light.
The low idling is not a big problem in general unless engine dies on you later during a ride when stopped at red lights or any other idling situation. It is annoying for sure - even if it happens only during initial start it should be investigated before things get worse (not sure they will, but just in case). My experience is that most of these "too low idle" situation are cause by either (in order of probability):
1) incorrect starting procedure: the throttle should always be closed at idle stop and should NOT be opened manually during starting phase (assuming the whole system is working correctly). I understand that now you need to keep it opened a bit AFTER start, but make sure you are not opening during start.
2) incorrect throttle cable free-play: specs / procedure to check is documented in CLYMER and on BMW shop manual. When there is not enough free play, it will confused the Motronic EFI system as what is the base reference at idle stop for TPS.
3) Defective or not well set TVA: the TVA is the idle-actuator that controls the fast idle when cold, and it also stabilized idle at all other times. This component has been very reliable, but there has been a few failure or bad behavior as it wears out (pretty mechanical device with a stepper motor and plastic worm-drive).
4) defective engine coolant temp sensor: this will confuse the Motronic-EFI system on cold start as it will use a default value of 80 celcius (176 F) when it sees any abnormal value after ignition ON. Failure are NOT common and when they fail you will often hear the radiator fans go on as soon as you turn ignition on (fail safe mode of the system)
5) Defective or not well set TPS: this component has also been very reliable in the past so unless someone did recent work around throttle-bodies, I would assume it is not the main cause.
Obviously, there are other possible causes related to general state of tune of the engine. I am assuming here that the rest is in pretty good shape (air-filter, spark-plug, plug wires, valves checked). AS ALWAYS: many problems are related to recent work done on a vehicle - can you relate your problem to such an event?
Not sure I fully understand from above post of bike is running fine and has good pulling power in all other running conditions - does it ??
What about the fuel-mileage - do you keep track at every fill-up and is it still the same as before ??
UNLESS I can see the bike and take some measurements, the only way to troubleshoot AT A DISTANCE some of these sensors (item 3, 4 5) is to gather real-time data using a GS911.
PROCEDURE TO LOG DATA INTO A FILE from a GS911 (Yellow unit using USB-cable): There is so many variables from machine-to-machine that it is important for me to gather this data in same conditions to minimize variables.
(1) Install K1200LT on center stand (do not start until step 4 below)
(2) Plug GS911 into bike diagnostic plug, then into PC (if Yellow unit)
(3) Start software (will ask ignition ON) and go into menu "realtime values" + "Log to CSV" button. Use defaults for all items. Choose / type a filename or use the default filename offered.
(4) Start your K1200LT. AFTER about 1 minute of IDLING do occasional throttle twist to raise RPM to 2000 (4 to 5 seconds) and 4000 RPM (2-3 seconds). After these short RPM changes let it go back to idle for at least 30 secs in between. During the starting phase, open throtlle manually ONLY if you see engine will die.
(5) Stop "log-to file" on screen interface, then stop engine when you reach above half-way point on the temp gauge on dash -OR- at least a full log time of 4 minutes.
See attached image for menu items in GS911 software. Screen may vary a bit depending on your software version.