EMB ERJ 170/175 ER/LR
Flight Crew Air Transport Pilot (ATP)
Time Pressure
Aircraft Equipment Problem Critical
General Maintenance Action
Aircraft
During the taxi out the First Officer informed me that the detent on the start/stop knob might not have been functioning 100%.  I thought about the night before (as we had brought in the same airplane) and when I shut down the Number 1 engine. The detent was functioning (albeit maybe slightly loose); but it seemed to be functioning correctly and preventing the knob from traveling on its own.  I thought this was what the First Officer was alluding to and decided to continue with the taxi out.  After thinking about it further enroute and in the interest of safety I decided to inform Dispatch that the start/stop detents might not be functioning 100% and perhaps it would be wise to have them looked at by Maintenance.  When we arrived at the gate I confirmed that the detents were in fact not functioning 100% and warranted a write up.  It should be noted the situation may have been aggravated further on the ground when I attempted move the selectors to stop without first pulling them up to confirm they were not functioning properly.  I believe this made the difference between them being slightly loose; and being inoperative.  Although the knobs were functioning correctly at departure; it might have been prudent to try and force them to stop without lifting them before we left to confirm that a little bit of looseness in the travel would not cause a problem.  Perhaps put more of an emphasis on safety than on-time performance.  A comment from the Mechanic that showed up to our airplane 'THANKS FOR GROUNDING THE AIRPLANE' does not help in the argument of whats more important.
EMB170 Captain is informed by the First Officer during taxi out that the detent for the engine start/stop knob may not be functioning correctly.  Upon arrival a quick test indicates that the knob should be written up.  The Mechanic who shows up chastises the Captain for grounding the aircraft.