I have a 2003 Mitsubishi Eclipse RS, 75000 miles, 2.4L. Last night my car would not start. I tried turning it over many times and there was nothing. When I opened the hood I heard a clicking noise. The ignition switch was in the off position. I opened the fuse box under the hood and the sound seemed to be coming from the ECU. It finally stopped clicking and I ended up getting a jump. I drove it home then turned the car off and tried turning it back on. Nothing. Today I purchased a new battery and installed it. I started the car just fine but its idling weird. It will idle fine for a second around (750) then decrease to around (500) and seems like it wants to cut off. Then the idle will increase again. The car was running fine before last night when the battery died. The only thing I changed was the battery and the negative battery cable was corroded so I had to change that also. Other than that the only other thing that was weird was the clicking from the ECU. At least it sounded like it was coming from there. Please Help!