Do you have a 1.6 or 1.8 engine? How well does the car run? How many miles? O2 sensors age? What spark plugs did you use?

 

1.6 engine. The car is running just fine as far as I can tell, it's got 158,604 miles. I don't know exactly how old the o2 sensor is, but I know that it is pretty new. I don't remember what spark plugs I used, honestly probably just the cheapest ones.

 

Is CO% 0.22% considered normal? What is the limit for that? The combination of high HC and high, normal or low CO% can shed light on the problem causing the failure.

You said you changed the head gasket which involves removing the timing belt and possibly the distributor. That and in your other thread you were asking about retarding the timing. This makes me believe you've never actually checked the ignition timing with a timing light. Is that correct? If so, buy/rent/borrow a timing light and check the timing. If it's off, set it to the correct value. If it's already correct, then you can think about retarding it, but I don't think that will solve the problem.

The repair manual says for high HC and normal CO% to check for incorrect ignition timing. It also says to check distributor, spark plugs, wires, but you've already replaced those. Also, incorrect valve clearance, leaky exhaust valves and leaky cylinder. I think ignition timing is much more likely than the last things I listed.

 

The standard CO% is 1.20, so im lower than that at 0.22. Yes, that is correct, I never checked the timing with a timing light, but for that to work doesn't there need to be the timing marks on the harmonic balancer? I think they are gone on my car, and when I set the timing, whatever I used to make a new mark I think it rubbed off, would this be a problem?

 

SO set it on TDC and make a new mark. Chalked marks have been around forever.

 

There should be a small V-shaped notch on the pulley/harmonic balancer. It is on the side near the timing belt cover. Since it is a notch, it shouldn't be missing. The mark is easy to miss unless you know what you're looking for. The timing belt cover has several lines at the 0, 5, 10, 15, 20 degrees before-top-dead-center (BTDC) angles.

The marks you made when putting the distributor in don't matter. You just need a timing light and the marks on the pulkey and timing belt cover.
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Found this thread from a search, so I'll add some info for future users.

1. adjusting ignition-timing won't affect HC, CO, CO2 emissions by much. It will affect NOx the most. More advanced ignition causes hotter combustion and will raise NOx. Retarding igntion will lower combustion-temps and lower NOx.

2. HC emissions are a function of fuel-to-air ratios. Vacuum leaks, fuel-pressure, injectors, etc. will affect the AFR regardless of ignition-timing.


My wife's '94 Corolla DX had a trend towards higher HC during the past 6-years (3 smog-tests in California). Two years ago, HC was right at the limit. Last week with recent test, it was over HC by +15%.

I found that the pre-converter right after the headers had the core crumbled mostly away with only about 10% of the material left. Replacing it with a used one from local junkyard restored HC scrubbing and it passed with HC at only 20% of limit. That's roughly an 90% reduction in HC emissions. Just make sure you inspect the original pre-converter to see if it's the culprit and confirm that the replacement is all intact and fully-functional.

 

By pre-converter do you mean the pre-cat on the header itself? Keep in mind that very few Corollas have that, that was a California standard. My federal Corolla (that lived its entire life in California) has only one catalytic converter, no pre-cat. Sticker under the hood states if it's federal or California model.

 

Yes, only California models have pre-cat and smaller catalytic later. The pre-converter takes advantage of higher-heat levels immediately after the headers for quicker activation of the catalytic when starting a cold-engine. Once warned up, both CA and 49-state models should have similar emissions.

Regardless of catalytic configuration, HC emissions aren't really affected by ignition-timing much anyway.

One thing to inspect with MAP-sensor based cars is vacuum leaks. Use a vacuum-T to tap into the MAP-sensor line and measure vacuum with warmed up engine. It should be in the 30-kpa (-20 in.Hg) range. Vacuum-leaks in the intake can increase manifold absolute-pressure and trick the ECU into thinking that the amount of air going into the engine is more than actual. This would result in the ECU injecting more fuel than normal and resulting in high HC levels.

 

Hi, this is interesting. I am currently having the same problem. I am failing on HC on the curb idle. I am getting results over 600 ppm HC at 750 rpm. I recently had my throttle body cleaned and it went down to 500 ppm, but still way over the 200 ppm Ontario limit. Plus I also have had my head cylinder completely rebuilt brand new, all new plugs wires distrib, all new exhaust, but yet still failing. Mine is also a 1.6L but mines a 97 so its OBD2. But I still have to get a tailpipe test.

I just recently dumped in a full bottle of Guarenteed to Pass when I was empty with the gas light on, then put in 10$ 87 octane, then went to town and filled up the tank with some 94 Octane.

Yes I'm a little nervous, but my friend guarenteed it will be fine, and it seems to be running just as good as ever. She's got a lot more power that's for sure! I'm going to burn this out then fill up with 89 then back to 87 then go for a test.