Connecting a 4iii left arm power meter (ANT +)

Very strange. I have the same power meter and the connection was straight forward. Download the 4iiii app on your smartphone, connect the power meter to your smartphone through the app and check for firmware updates. 

I spun my cranks about 5 times to ensure the power meter woke up. Paired it to the 4iiii app, did a firmware update, then paired to Edge 530. The Edge saw it and connected almost immediately when selecting the power meter. On firmware version 3.2.0.

I just did it now again to make sure it worked for me, and it did 

Hello- as you have the same power meter as me, can you please let me know if you get erroneous maximum cadence readings?

I have regular spikes reporting and thus the maximum cadence for a ride is always 160-200+ due to these spikes. I can understand one or two spikes in the course of a long ride but this is regular. 

I’ve ridden with the Stages left power meter and a Garmin cadence sensor and neither have this problem. Maximum cadence never exceeded 110-115, etc. 

I have actually seen this as well, but not always. Some rides in the past have shown a max cadence of 200+ as a statistic, but looking at the graph there is no indication of when that might have been recorded

In Strava, if I isolate the ride to 1000km segments and analyze, there are spikes almost every single time I zoom in. They're extremely common, usually at least 1-2 every 1km without much rhyme or reason. I could be going a steady 90 rpm and suddenly it spikes to 130 and back to 90.

Same happened to me.  I called Gamin and all you need to do is scroll up to "Add Sensor" to highlight it and then select it and that adds the sensor.  After that you can also do a calibration. 

Did you find a solution to this as I am currently having the exact same problem

The solution for me was to upgrade to a Garmin 1030P.  No issues on that.