Reducing HC Emissions After Smog

[jeff88]

I got my car smogged today. It just barely passed the maximum HC limits at 15MPH. Max is 64 and I passed with 63! Phew! At 25MPH, it was nowhere near the limit.

So for another 2 years, I'm off the hook. But I am trying to stay ahead of the game, so I don't get any shockers at the next smog check. Is there anything aftermarket I can add/change/clean/do that can help lower the hydrocarbon emissions (or any of the other emissions, for that matter) or is there something I should double check to see if it is about to fail, but hasn't necessarily thrown a code yet? For example, should I double check my EGR system to see if the valve is operating properly? Will cleaning the intake and/or exhaust manifolds help lower emissions? Will some sort of cleaner to "clean" the cat be of benefit?

Even without the smog test, I would like to keep the emissions as low as possible!

Also, as a side note, I thought it was interesting that the car was tested at 15MPH @ 1738 RPMs and 25MPH @ 1740 RPMs. A whole 2 revolutions difference! (I assume it has changed gears somewhere between 15 and 25)

[2000mc]

I'd heard from other techs the o2 can be problematic. I never work on corollas, but the last time I worked on a prism I fixed a lean code with an o2, there wasn't any other codes

[baldlobo]

your dealing with unburnt fuel; try testing your o2 sensor(s), coolent temp sensor, intake air temp sensor; if that doesn't help you might have a leaking injector

[Occasionally6]

Yes, O2 sensor. They have a life of about 50 000 miles, give or take a bit.

Maybe look at the basics like spark plugs and ignition leads. The 'plugs will typically have a life of about 30 000 miles. The leads are replace as needed. When you buy your DMM, you can check their resistance. They should be < 3000 Ohms per ft.

An ignition misfire might or might not show up as a fault code. If it's happening, it can be hard on the cat. so it's worth checking the leads and the 'plugs are cheap, if there's any doubt.

Engine oil can load up with fuel over time so, an oil change can help sometimes.

If you have a fuel tank vent system with a Carbon canister purge valve, it's possible that may be leaking.

If the engine has wear on it and is burning oil that will increase the HC. (A higher viscosity oil might get you past the test if it's marginal.)