For those of us with older engines and black box ECUs...

The TPS is a mechanical rheostat style unit which outputs a voltage signal to the ECU corresponding to throttle position.  It seems that over time the mechanism can develop wear in certain positions (likely from frequent range of use or vibration related to throttle cable routing and attachment to throttle body.)  This can result in a bit of stumble or hesitation in the engine with throttle movement depending on "where" the wear has occurred. In my recent situation, this stumble was happening in the 1500-1600 rpm range - the range I'm usually at during my base and base to final turns as well as mid to short final portions of my landings.  Other than in the range of wear, engine operation and response to throttle movement is normal and as expected. 

One fix is to replace the TPS - the new one will required calibration and is something that Ray Lawrence (ULP maintenance) can acomplish and what I have elected to have done. The more expensive fix is to replace the throttle body to accomodate the modern Hall effect type TPS and send the ECU back to ULP for reprogramming.

The newer 4 cyinder engines (2018 and on ?) have the more modern Hall effect type sensors and should never have this "wear" issue. Acccording to Ray, all the 6 cylinder engines incorporate the Hall type sensors. 

More info to follow after replacement accomplished.

Dave

Sky Turtle 826DE

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Update...

Throttle body with calibrated sensor received from ULP Belgium last week.  Installed and problem fixed.  What I did learn from this (or relearn?) is that with my setup of dual ECU and associated sensors is that both ECUs share this one and only throttle position sensor (TPS) - again I have the old style black box ECUs.  The newer engines with dual ECUs have a double Hall type TPS which I believe is an improvement in overall redundancy.

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