i've been having some minor problems with my car after motor rebuild... the car is not turboed yet, will be in a month or two.. ive got my sfac 2 installed and realised that my problem can be related to battery voltage but not sure so i thought you guys can help me out..

the problem is i dont get full performance sometimes without any reason and sometimes the idle drops like its missfiring or something else.. after the installation of the safc i realised that when the idle dropping happens i get like 13.5 volts reading from the safc 2 and when i turn on my heating fans it drops to 13.3 then the car starts shaking. mostly i read a voltage of 13.8.. but sometimes i get 14.1 volts and at that time the car runs pretty good and feels clean.. but as i said its around 13.8 volts most of the time and when i go wot it drops to 13.6 at high revs..

im not sure if this is something normal probably not but what could be causing this? can it be because of a bad alternator?

 

13.6 is normal

check your grounds