ESP8266 Community Forum

The ESP8266 can draw up to 170mA whilst the maximum current available from the the Uno's 3.3V pin is 150mA so your arrangement is marginal at best. I'd suggest a better psu for your ESP, they're cheap and readily available.

I would second that it is most likely your power arrangements causing the problem.

Note that even 170mA is not enough. Although the normal average current draw is about 80mA the esp8266 can draw bursts of about 400mA. It is recommended to use a power source that can supply 500mA and it is also good practice to add a decent reservoir capacitor close to the esp8266 module to smooth out the bursts of current.

thanks for the replys any idea what rating of cap?

Bigger the better, I usually go for 1000uf