Low idle/stumble at start up

[kalali]

1999 R1100R with 18K miles. The bike always starts on the second try with the choke on. It idles at around 1500RPM but gradually drops down on its own to about 1100RPM and then starts creeping back up to about 1800RPM, again on its own, as the engine warms up and stays there until I close the choke and ride off. This only happens at cold starts and never on warm restarts. After this initial stumble the idle stays rock solid at 1100RPM throughout. The only clue is a bit of gasoline smell when this behavior is in progress and this makes me wonder if maybe the injectors are seeping overnight and the bike stumbles while this excess fuel is burnt of. Does this make sense or there's something else causing this behavior? Is there an easy way to confirm leaky injectors, e.g., remove the fuel line to the injectors overnight, etc.? Thanks in advance.

[dirtrider]

1999 R1100R with 18K miles. The bike always starts on the second try with the choke on. It idles at around 1500RPM but gradually drops down on its own to about 1100RPM and then starts creeping back up to about 1800RPM, again on its own, as the engine warms up and stays there until I close the choke and ride off. This only happens at cold starts and never on warm restarts. After this initial stumble the idle stays rock solid at 1100RPM throughout. The only clue is a bit of gasoline smell when this behavior is in progress and this makes me wonder if maybe the injectors are seeping overnight and the bike stumbles while this excess fuel is burnt of. Does this make sense or there's something else causing this behavior? Is there an easy way to confirm leaky injectors, e.g., remove the fuel line to the injectors overnight, etc.? Thanks in advance.

 

Afternoon kalali

 

You would think that IF you have a dripping injector that it would act up from the get-go not after running for awhile.

 

Does your bike still have the original CCP in it? If not then try reinstalling that, then removing fuse 5 for about 5 minutes, then reinstall fuse 5.

 

You might have one of those 1100's that will act like yours is for life-- There was a BMW service bulletin on the 1100 that talked of certain engine sensor inputs lining up to produce a cold stall and/or a poor cold idle after a short run time.

 

You REALLY should not warm up a BMW boxer engine, just start it then ride off easily. Warm up has no real purpose except to burn /discolor the tupperware above the exhaust pipes.

[kalali]

 

You would think that IF you have a dripping injector that it would act up from the get-go not after running for awhile.

 

Does your bike still have the original CCP in it? If not then try reinstalling that, then removing fuse 5 for about 5 minutes, then reinstall fuse 5.

 

Hi dirtrider, thanks for the input. The bike actually acts up at cold start not after running for a while or at subsequent warm start ups. That's why I thought may be the injector(s) is leaking a little bit of fuel and causing the initial stumble. It never stalls. As for the CCP, I still have the original pink CCP and never removed it. The only reason I warm up the engine is I'm worried it might stall when I leave my driveway if I don't wait long enough for the engine to settle into a steady idle. It really just takes a minute or two for the engine to "clear its throat" so to speak.

[kalali]

Just a quick update. I removed the brass screws and cleaned them along with the intake passages before starting up the bike today. The engine speed did drop a little like before with choke on but this time it recovered a lot more quickly and maintained the high idle. I had cleaned them last year, roughly 2K miles ago, but there was a tiny bit of soot on both, a little more on the one on the right cylinder. I'm not too concerned and think this is probably a side effect of riding the bike mostly short distances or winter grade ethanol gas here in Northeast. I'll increase my Techron fuel injection cleaning routine going forward.