Passed Smog Test By 1 Ppm Hc

[blkstanger]

So I had to smog my car today as I live in Ca. On the 15 mph test I was 1 ppm away from failing. It was the HC that was high. Everything else was ok and not close to failing. The HC dropped for the 25 mph test.
So what would cause this? Do I just need a tune up or something else? I was thinking that the o2 sensors might be getting lazy. But I don't know what exactly the test result mean or how to diagnose. Someone said to clean the tube that runs from the exhaust to the EGR but I don;t know. Any other ideas?
The car now has 160k on it and is stock. Just changed the oil. Plugs and wires are two years old. No other issues, CELs or any other problems.

 

[trinity_gt]

So I had to smog my car today as I live in Ca. On the 15 mph test I was 1 ppm away from failing. It was the HC that was high. Everything else was ok and not close to failing. The HC dropped for the 25 mph test.
So what would cause this? Do I just need a tune up or something else? I was thinking that the o2 sensors might be getting lazy. But I don't know what exactly the test result mean or how to diagnose. Someone said to clean the tube that runs from the exhaust to the EGR but I don;t know. Any other ideas?
The car now has 160k on it and is stock. Just changed the oil. Plugs and wires are two years old. No other issues, CELs or any other problems.

HCs are unburnt hydrocarbons. It's not caused by lack of EGR flow so don't worry about that. (If you saw high NOx numbers I'd say to look at it...)

HCs are caused by one or more of:

• excessive fuel
• oil making its way into the combustion chamber
• ineffective catalytic converters

Questions:

1) Is the factory midpipe still in place?
2) Does the car burn oil?
3) How old are the O2 sensors?

 

[blkstanger]

It's all stock exhaust, Uses very little oil. Maybe a qt in 5-6 thousand miles. O2 sensors are probably the originals as far as I know. I have only owned the car two years.

 

[trinity_gt]

If the O2 sensors are old you might consider going ahead and replacing them. These sensors really should be considered wear items and replaced at 80K to 100K mile intervals at most.

High HC readings can also be attributed to partial or complete misfires. You might check the plugs while you're doing other maintenance.

 

[PULMEOVR]

Just curious, what were your limits in regards to NOX, HC, etc? I'm in Ottawa and I think our emissions standards are really similar to yours in California.