I have a 96 cx hatch with a b17 swap (b16 head and pistons)

I notice when ever my gas is low my car idles low, like 700-750rpm, someitmes 550-600 .. but it stays steady where ever it's at.

i used to run 87 and it idled low all the time, now i run 93 and it only idles low when my gas is low. If i have a quarter tank or higher, my idle is about 900rpm

what could this be ?? Normal ?? Let me know what ever else information you need.

 

It sounds like you have a weak fuel pump. Try using a gas treatment chemical and see if that fixes your problem. If not id suggest a new fuel filter.. then work your way up to a new fuel pump

 

or you can test the fuel pressure and see if there are any issues there.