How can I diagnose what is interfering with my Wifi signal?
A request timeout on ICMP (ping) going from your Mac to your your network device simply means that the device, not your Mac failed to respond to the ping request in a given amount of time.  There is a good explanation of that here.

This can happen for any number of reasons; network congestion, device load, wifi signal interference, power loss, etc.  Most importantly, it has absolutely nothing to do with services that are running on your Mac.  

Based on the address you used, it looks like you are pinging google.com.  This means that between your Mac and Google's servers there are a number of "hops" that your packet must go through.  Your Mac to your Wifi is one hop.  Wifi to your router/modem is another hop.  Modem to your providers gateway is another hop and so on until you get to Google.

To see how your hops are performing, issue the command traceroute google.com and it will output something similar to the following:

    1  pfsense (192.168.10.1)  0.401 ms  0.176 ms  0.223 ms
     2  96.120.36.197 (96.120.36.197)  23.503 ms  8.269 ms  8.470 ms
     3  xe-1-3-0-0-sur02.miramar.fl.pompano.comcast.net (68.85.82.157)  9.371 ms  8.740 ms  8.517 ms
     4  xe-11-2-2-0-sur03.miramar.fl.pompano.comcast.net (69.139.183.46)  10.091 ms
        xe-11-2-0-0-sur03.miramar.fl.pompano.comcast.net (69.139.183.14)  20.572 ms
        xe-11-1-1-0-sur03.miramar.fl.pompano.comcast.net (69.139.183.177)  9.440 ms
     5  te-9-1-ur01.wellington.fl.pompano.comcast.net (68.85.219.25)  16.879 ms  9.370 ms
        xe-1-0-7-0-ar02.stuart.fl.pompano.comcast.net (68.85.219.29)  16.575 ms
     6  be-20214-cr02.miami.fl.ibone.comcast.net (68.86.90.205)  10.963 ms  12.427 ms  11.617 ms
     7  68.86.82.74 (68.86.82.74)  10.475 ms  11.337 ms  9.979 ms
     8  23.30.207.242 (23.30.207.242)  47.521 ms  45.935 ms  47.899 ms
     9  209.85.241.136 (209.85.241.136)  10.958 ms  10.625 ms  10.479 ms
    10  216.239.42.79 (216.239.42.79)  10.616 ms  11.121 ms  10.590 ms
    11  mia07s35-in-f14.1e100.net (216.58.192.110)  17.763 ms  16.857 ms  11.290 ms
traceroute to google.com (216.58.192.110), 64 hops max, 52 byte packets


That's my currently traceroute for Google.  Yours will definitely be different.  Either way, anything in between could be contributing to a dropped packet which is the request timeout error you are seeing.