just started having same issue as you within the last week.
spent 460$ on a new router and modem
ive had 3 cox (isp) techs out to my house
no luck...
just random spikes... ill go from 7ms to 280ms randomly...
will let you know if i find a solution....
PING www.google.com (216.58.216.36): 56 data bytes
64 bytes from 216.58.216.36: seq=0 ttl=56 time=21.033 ms
64 bytes from 216.58.216.36: seq=1 ttl=56 time=21.071 ms
64 bytes from 216.58.216.36: seq=2 ttl=56 time=22.657 ms
64 bytes from 216.58.216.36: seq=3 ttl=56 time=21.085 ms
64 bytes from 216.58.216.36: seq=4 ttl=56 time=19.062 ms
64 bytes from 216.58.216.36: seq=5 ttl=56 time=19.736 ms
64 bytes from 216.58.216.36: seq=6 ttl=56 time=474.055 ms
64 bytes from 216.58.216.36: seq=7 ttl=56 time=243.685 ms
64 bytes from 216.58.216.36: seq=8 ttl=56 time=224.962 ms
64 bytes from 216.58.216.36: seq=9 ttl=56 time=28.787 ms
64 bytes from 216.58.216.36: seq=10 ttl=56 time=39.125 ms
64 bytes from 216.58.216.36: seq=11 ttl=56 time=19.061 ms
64 bytes from 216.58.216.36: seq=12 ttl=56 time=24.213 ms
64 bytes from 216.58.216.36: seq=13 ttl=56 time=23.507 ms
64 bytes from 216.58.216.36: seq=14 ttl=56 time=23.436 ms
--- www.google.com ping statistics ---
15 packets transmitted, 15 packets received, 0% packet loss
round-trip min/avg/max = 19.061/81.698/474.055 ms