Acceleration stumble when cold

[H2oskier13]

I have a 13 Reaponse TXI with the Monsoon 350 SS engine. When accelerating cold to pull a a skier up the engine rpm drops momentarily and then picks back up. This only ever happens when it’s cold on the first run of the day. It has never acted up any other time. With no skier and cold I can make it happen once on the first pull but cannot make it happen again even if I immediately stop and go again. 

Any ideas?

Edited May 5, 2018 by H2oskier13

[skurfer]

When is the last time you cleaned your flame arrestor and the flap underneath? Also, when is the last time you changed your fuel filter, cap/rotor/spark plugs?

[H2oskier13]

I’m not sure what you mean by flame arrestor, I have an air filter and it is clean. As for plugs, cap, rotor and fuel filter they are all original. If there was a problem with one of those items I would expect the stumble to happen more often than only when it is cold on its initial acceleration run. 

[Woodski]

@H2oskier13:  When the intake tract is cold, the fuel has trouble atomizing with the cold air so I would look towards the fuel system - a dirty injector would shoot a less atomized mixture compared to a clean one which would lead to a stumble condition.  You might want to have the injectors cleaned.  Do you warm up your engine before that first pull or start you ski run only after idling to the start point?  As your ignition parts age, it will take more voltage to create a good spark, so corrosion on the cap and worn plugs (increasing the gap) will contribute to cold operation issues.

[electricjohn]

Loose hose or vacuum leak on the intake system contribute to hesitation.

[JasonK]

Do a tune-up. It's due for one.