to which wire do i hook up my air/fuel gauge(99 civic ex t3 turbo), their are 2 black, one green, one white which one is signal wire. Also Having problems with the engine overheating, coolent starrts boiling then starts 2 leak from resovror tank. whats the problem, radiator, thermostat, i am trying 2 figure it out. Any sugestions.

 

White wire is your o2 signal voltage wire. With your overheating problem try to replace the cheap stuff first put new coolant in with the correct mixture of water/coolant. Radiator cap and thermostat are also good to put on new then go from there.