Soon after my purchase of the 500 HO EPS, I noticed the previously documented, low speed sudden drop off of power around the 3,700 - 4,200 rpm range. Quite annoying.

After researching a bit online and querying my dealer, I simply backed out the idle speed adjustment screw to achieve +/- 50 rpm's of 1400 rpm idle speed.  I can no longer duplicate the issue.

I believe it is related to why you never depress the accelerator while starting an EFI vehicle.  Whatever position the Throttle Position Sensor is in at startup dictates how the EFI Map will be applied. On mine, the throttle stop position was higher then normal, and apparently caused the sudden deceleration while in the 3,700 - 4,200 rpm range.

There has been conversations about modifying or re-mapping either the ECU or TPS. I do not believe either of these steps are needed.

I didn't actually back out the idle speed adjustment screw- I replaced it with a 5mm bolt and jam nut. The idle speed adjustment screw is of low quality material, and has a Phillips head-now partially stripped when I attempted to remove the jam nut. The 5mm bolt is now easily adjusted with an 8mm Gearwrench. However, I assume adjustment is unnecessary once set.

Hi, I just purchased a Cforce 500 HO and experience the same issue.  When you talk about the idle screw,  are you referring to the  speed limiter screw at the back of the thumb throttle? 

[2015 Z Force 800 53/Trail EPS]

Hi, I just purchased a Cforce 500 HO and experience the same issue.  When you talk about the idle screw,  are you referring to the  speed limiter screw at the back of the thumb throttle? 

I believe they are talking about the one on the throttle body.

What is the screw on the back of the thumb throttle a govenor screw?