Failing CA Smog test, Need help

[Boifilm]

I have a 93 Corolla 1.6L stardard trans. I took it for a smog check because I need to do so in order to renew the registration. However, it failed the test.

At first, it failed because the level of NO was too high. Good thing I went to a “pass or retest for free” place.

Around that same time a check engine light came up. The code was Error 71, which has something to do with EGR. I did some research online and all this made sense because a bad EGR is something that will cause elevated NO level.

So over the weekend I took off the EGR and clean it out, and made sure nothing was clogged. Once the EGR was installed again, I can feel a noticeable difference in the car. The car seems to run smoother. Thinking that I’ve solved my problem, I took it back for a re-test.

When the re-test was done, it failed again. But the strange thing is that the NO level is ok, now the HC level is over the limit at 25MPH/~1900RPM (I believe the MAX acceptable level is 59ppm, and I think my result was 71ppm for the corolla).

I don't know much about troubleshooting emission problems, so can maybe some help me explain this? Does it make sense that fixing the EGR would lower the NO level but increase the HC level? Anyone had similar problems?

[retiredat44]

I have no clue but my Cat converter usually fails

[Bitter]

whens the last time you replaced plugs, wires, cap, and rotor? does the engine reach 1/2 way on the temp gauge? poor ignition components or a cold engine can cause high HC. you may have had high HC and high NOx before, but they flagged and failed you for the highest one.

a bad cat can also cause high HC, but go after the simple and cheap things first...it probably needs them anyways.

[Boifilm]

plugs, wires, cap, rotor were replaced about 2 years ago, which was I think less than 10,000miles ago. they should be still good. But just in case, I'll go get some spark plugs and replace them tomorrow, they are not that expensive anyway. It was a mechanic who changed the plugs last time, I haven't even checked them since. So thanks for the tip

As for the temperature, I had to drive quite a few miles to the smog test location, so the engine was definitely already warmed up.

I think what I'll do now is 1)change the spark plugs, and 2)clean the engine with Seafoam.

I read on another forum that someone clean the engine with Seafoam and it helped his car pass the smog test. My corolla didn't fail the smog test by too much so hopefully these 2 things would help get it pass.

[Bitter]

i understand that you think the engine was all the way hot, but a sticking open thermostat can cause it to run cool and the engine to richen the air/fuel ratio and then you fail with high HC. the temp should be about 1/2 way on the gauge after 1-2 miles of normal driving with no warmup anytime its warmer than 40 degrees outside, sooner if its warmer out. even a bad temperature sensor (sender is one wire, sensor is 2 wire) can cause a high HC and rich running, but thats less common than a worn out thermostat. so i ask again, when you tested, where was the temp needle?

[Boifilm]

I don't remember exactly where the temperature gauge was pointed when I got to the testing place. But usually when I drive the temp gauge would point a little bit below the half way mark once it warms up. The place that I take it to do smog test is about 6~7 miles away.

So are you are suggesting the thermostat might be bad?

Anyway, I seafoam the engine yesterday. I was surprised that it really makes a noticeable difference. The engine now runs a lot smoother.

[Bitter]

nah, that sounds about like where the needle should be. i was just making sure though, because you could throw ALOT of money at a problem when it was as simple as a bad thermostat.

[Boifilm]

Well, I Seafoam the engine and changed the spark plugs. So today I took it in for another smog test. But now the guy tells me the car does not have enough power to perform the test. WTF? Like I said before, the car drives smoother now, and I don't feel any problems driving it. I drove 75mph on the freeway, I drove over some hills (I have to drive over a hill to get to the smog test place), I just don't see any problem with the car. It doesn't make sense, it's frustrating, and it feels like he is just BS'ing me. But I don't know anything about the test procedure to disagree with the guy. Plus I don't see any reason why he would want to lie to me, I've taken 3 other cars to have him test before in the past, and never had any problems.

So anyone here have any opinions on this? Does it require a certain amount of HP or Torque to get the smog test done?

[Bitter]

no, the 4afe more than has enough power to roll the dyno.

[kevmac]

Was there ever a cel?
What did you seafoam? vacuum hoses? gas? oil? throttle body?
If you seafoamed a very dirty fuel system via vacuum hose, you may want to pull the plugs to clean the junk that may be on them. Is the car idling fine? Is there any sign of exhaust leak? The seafoam would have shown this if done through the vacuum hoses.

check:
air filter
egr modulator
exhaust leak
cat


Maybe someone else can comment, but won't the symptoms you claimed disappear after a new CAT install? The universal cat will bake the unspent fuel. I forget what else is tested though. Funny, I have to test my car on Monday.

If you decide not to replace the cat, then at least bake it before the test. Drive hard for 30 to 60 minutes with ac on high. Get that engine as hot as possible.

Edit: That may be your problem. It is cold in so cal now and you might be going in with a cold cat.
?

[Boifilm]

THE CEL was on before. It gave an error 71, which indicates a problem with the EGR. I've since clean the EGR and the CEL went away.

The spark plugs were replaced after Seafoam. And the car idles fine. Both cleaning the EGR and Seafoam seemed to improve idle (quieter and less vibration).

So the exhaust should be completely sealed all the way through both O2 sensors?

If so, I think you might be on to something, there might be an exhaust leak. I Seafoamed through a vacuum line (from the brake booster), When I did that, I have some smoke coming out between the exhaust manifold and the engine. I thought that might not be normal, but there was just a little bit of smoke and the car seems to run fine afterward, so I ignored that little bit of observation (as you can see, I am not an experienced mechanic, in fact, back before I own this Corolla I was afraid to work on cars).

When there is an exhaust leak, it would cause the engine to run rich right? how about power, it would cause power loss too?

[Bitter]

its very very common for the stock cast iron manifold to crack between cylinders 2 and 3. remove the heat shield and take a look there. it can cause a lawnmower like noise under acceleration as well as make the car run rich or lean since the O2 sensor is not getting all of the exhaust to read as well as some power loss.

replace the manifold, they're pretty cheap on ebay.

[kevmac]

Sorry if I missed it, how long are you running the engine before arriving to the test? You mention HC, NO, lack of power, exhaust leak. I think HC and NO are high or low fuel levels (in other words, fuel not burned off). I bet if you changed the exhaust manifold and CAT, you will be whole

Check ebay for header too.
http://cgi.ebay.com/ebaymotors/93-95-96-97-TOYOTA-COROLLA-STAINLESS-EXHAUST-HEADER-1-6_W0QQcmdZViewItemQQhashZitem53da89b275QQitemZ3601 48742773QQptZRaceQ5fCarQ5fParts

[Bitter]

he won't pass visual with that ebay one there. he needs an OEM type manifold.

[kevmac]

good to know if true because I planned to get one when mine goes out.