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Stalling after TB sync


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A new problem has surfaced since I cleared the blocked air/idle screws and did a TB sync. The engine has a tendancy to stall suddenly when just off idle a couple of minutes after a cold start.


For example, if I blip the throttle, the engine can stall with no warning. Or pulling away from a stop, into a turn down hill, where the throttle is only open a bit.


This clears when the engine has thoroughly warmed up. I pulled the fuse on the motronic to reset, but it doesn't seem to have made any difference.

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Make sure your vacuum hoses are attached on both sides. If you have dual sparks, be sure the plug wire is fully set.


I had these same symptoms when I first got my bike.


BMW dealership performed the 24,000 major service before I took ownership. I discovered the left side vacuum sink hose disconnected and the right side secondary sparkplug was not attached.


I am now doing my own maintenance through help hear on this board.


Hope this helps.

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Glen, you really need to tell us what motorcycle you are working on.. If you are working on the 1100 you have in your signature line then there is NOTHING in the Motronic that will re-set when pulling the fuse..


Now on your stalling problem?


What is your TPS set at? Measure this with TBI throttle cam FIRMLY against the idle stop & make sure the fast idle ever is completely off.. If not under .4 volts it can cause a stalling problem under some throttle up conditions.. Maybe also track it’s voltage SWEEP from idle stop to about ½ throttle..


If your BMW has an 02 sensor try disconnecting that (as a test) as those can sometimes cause a problem like you are seeing as it warms up..


Are your throttle cables loose enough to FULLY allow the throttle plates to return to the idle stops?


Look for any vacuum leaks between the TBI & the cylinder head (use an unlit propane torch to look for vacuum leaks)..


Make sure your AIT (air intake sensor) on top of the air cleaner cover is firmly plugged in & the terminals are actually making good clean contact (I have seen a few with the contacts spread enough to not make good contact)..


Makes sure the 02 sensor wire (if you have one) is not near or contacting the R/H spark plug wire..


Do you have an open type exhaust on that bike? If so maybe you are getting enough reversion (negative wave) to shove spent exhaust gas back into the cylinder head & fouling the combustion process..


Maybe re-check the TBI balance in the range you are seeing the stalling..




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Thanks, Twisty. It's a '96 r1100r (the pic in my avatar). I will check the TPS, but have not done that before. Will look up the procedure. No dual spark. No O2 sensor. Throttle plates seem firmly closed. Stock exhaust. I'll also work though the other suggestions.


One additional symptom, is that on restart it smokes a great deal. This is interesting, because it does not normally smoke on startup. But on restart, it smokes profusely for a couple of seconds. Is it running really rich? Is that a clue?


What are the symptoms of an injector going bad? This bike has 61K miles on it.

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Glen, what color is the smoke? If black then possibly a dripping injector or something causing the Fueling Computer to call up a rich condition..


If blue the it is oil smoke & not fueling related..


Injectors can fail in a lot of ways- like plugging spray holes,, or the pintle not working correctly,, or not shutting off completely,, or dripping while parked..


Maybe have someone ride behind you when it stalls to see if it smokes black just before it stalls..


Clear the TPS as being a problem then determine if you have an injector problem..


Just a thought: If your bike has been fitted with quick disconnect fuel line disconnects make sure the return connector is COMPLETELY plugged together .. If it isn’t that will drive high fuel pressure.. Does your fuel pump sound like it is laboring?


How do your spark plugs look? Are they the same color side to side? If one side is real black & coked looking suspect a problem on that side..




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The smoke colour is black.


I pulled the plugs and the right side is more of a tan color than the left side. The left side insulator is whiter than the right. The right side had the clogged air/idle screw.


No quick disconects. The fuel pump sounds normal.


Will look at TPS next and clean the contacts on the air cleaner temp sensor.

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So far, the preliminary ride with the TPS set to .385 shows a huge improvement in overall running. Low RPM response is much improved. The bike always suffered from a decel 'lurch' when braking to a stop in gear as the RPMs passed through about 2500. That lurch appears to be gone. Throttle response is much smoother coming out of turn in second gear.

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Preliminary ride after pulling the CCP block entirely shows an incremental improvement in throttle response smoothness at lower RPMs, and up through cruising range. I am going to leave it out for a while see how it works longer term.

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