You'll need to also look at the CO emissions which your Mitsubishi Eclipse produced during the smog check. HC is raw fuel (gasoline). High HC means raw fuel is leaving your car's tailpipe when it should be burned in the engine.
It is important to know if your Mitsubishi Eclipse is in proper fuel control. Air/fuel mixture must be 14.7:1 in order for fuel to burn efficiently. By looking at the CO emissions which your car produced during the smog test we can ascertain approximately where the fault is that's causing the high HC failure.
If CO emissions where also high during the smog test, it is very possible that your Mitsubishi is producing high HC due because the fuel mixture is too rich. If CO is low, then the opposite applies; the air/fuel mixture might be too lean.
We have to recommend a hands-on diagnosis by a smog check repair station. The smog repair station will need to ensure your Mitsubishi is in proper fuel control, and that air/fuel ratio is as close to 14.7:1 as possible. During their diagnosis, the smog check repair technician will check all emission components which are responsible for sensing air intake, oxygen levels in the exhaust, and fuel delivery, as well as whether your vehicle's computer (ECU) is receiving and interpreting sensor data properly. The oxygen sensor must be diagnosed for proper operation, along with a very important fuel management component; the mass air flow sensor (MAF). Inspect the MAF (Mass Air Flow) sensor for proper operation. The MAF sensor will collect dirt and dust over time and should be cleaned, if not replaced. The MAF sensor is responsible for telling the ECU how much air is entering the intake manifold. An inaccurate reporting MAF sensor will absolutely cause a fuel mixture problem.
For high HC faults not related to fuel control, the most typical faults have to do with improper spark delivery caused by a defective or damaged ignition system components. We are referring to your Eclipse's spark ignition system; not to be confused with the key ignition system.
Read more about high HC problems... What causes high HC?
