Ram Speed PC Build

[Smokescreen]

Hi I built my first PC a little while ago. With It my friend gave me some ram just to get started. I just recently purchased some Ram 
G.SKILL TridentZ Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3866. Throught  aida64 the test fails if I put the ram at its rated speed. I just xmp in the bios and it when to 3866. Did I get bad ram, is it like it can run "up to that speed", am I doing a setting wrong? 

The rest of the pc is gigabyte z170 gaming 7 and i7 6700k

[Guest]

2 minutes ago, Smokescreen said:

Hi I built my first PC a little while ago. With It my friend gave me some ram just to get started. I just recently purchased some Ram 
G.SKILL TridentZ Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3866. Throught  aida64 the test fails if I put the ram at its rated speed. I just xmp in the bios and it when to 3866. Did I get bad ram, is it like it can run "up to that speed", am I doing a setting wrong? 

The rest of the pc is gigabyte z170 gaming 7 and i7 6700k

when you disable xmp, what does it run at?

[Smokescreen]

2133.

I just tried a setting it the bios called enhanced stability. Seems to be doing ok in short aida 64 tests. If I buy I higher rated ram speed am supposed to get that speed?