I charged my AC system tonight via the can instructions and the maintenance manual. Manual calls for 28oz for 93 miata. With R134 you are supposed to use 85% of this amount.

Which worked out to two of the 12oz cans.

I can't get the car to idle with the AC on, and it seems like the compressor is overly demanding while the AC is on.

Does this sound like an overcharge? The pressure was on the high side of the included gauge, but I felt that the maintenance manual value would be more accurate.

Good news is that it is blowing cold while on. However, I will have to turn the AC off when coming to a traffic light :(

 

Was the system completely empty and under vacuum before you filled it?

 

sounds like a way over charge. you only need about 33 pounds when the compressor is on. i over did mine once and had to buy a used one

 

It was completely empty, and the car was on with ac on per the instructions.

I just looked at the gauge. It appears by both the manual and gauge I should be ok. ~24oz of R134 and the gauge says 50lbs if outside temp is 85 degrees or above, which it was.