First off, let me just say that I am not too experienced with working on cars, but I'm trying to learn, and as such, I woul appreciate your responses to be in laymen's terms as much as possible.

I drive a '99 Honda Civic, and I recently got CEL codes 41 (primary oxygen sensor heater) and 90 (evaporative emission control system leak detected in the fuel tank area). I have also noticed that the car has been idling very rough, particularly when I am coming to a stop after maintaining a high rate of speed for some time.

I looked at the gas cap and filler neck opening, and didn't see the slightest indication of rust or degredation, so if I have a leak, I think it must be elsewhere. Also, when I remove the gas cap, it hisses, which seems to indicate that the tank is maintaining pressure (although I could be wrong). Any help you guys can give would be a huge help...money is tight, and if this is a problem I can resolve on my own, I would love that. Thanks in advance.

 

Unplug the primary sensor (the one first in line, closest to the engine) and measure resistance between the two wires that are the same color, which is the heater circuit. It should be something like 10 to 40 ohms. If it is open circuit, sensor is bad and needs to be replaced.

If it's not the gas cap you may need to have the fuel system "smoke" tested for leaks.