I hate failing smog on the borderline

[tadaima]

Getting real tired of this SMOG stuff.

Took in the car 4afe 4cylinder Geo Prizm (Toyota Corolla) engine.

Failed Gross polluter on NOX at 15mph

15mph
HC 110/130
CO .51/.80
NOX 2298/835 gross polluter

25mph
HC 139/105 failed
CO .38/.69
NOX 269/774

Well figured the Gross polluting was EGR based, so I cleaned the EGR and also found that the EGR modulator's filter was DIRTY!!!

Spark plugs have 2K on them
Oil has about 800miles on it
Went to put in the "Guarenteed to pass smog stuff"
Changed the air filter
Dist cap/rotor wires are 500miles new
Filled with Cheveron Premium

the only thing left are the O2 sensor and Catalytic convertor

Results are:

15mph
HC-128/130 went up by 18ppm
CO-.28/.8 went down by .23
NOX - 362/835 went down by 1936ppm!!!

25mph
HC -131/105 went down by 8ppm
CO -.33/.69 went down by .5
NOX - 203/774 went down 66ppm

02-0.4
CO2 - 14.8%

The only that bothered me was both times the car had to sit around for about an hour before it was tested. They said that they idle the car before it get into the dyno and kinda run it too.

Any suggestions? Or should I just eat it and get a new cat or 02 sensor?

Kinda sucks when i'm failing due to 26ppm og HC at 25mph

Thanks everyone

 

[The_Jeff]

Maybe a few bottles of drygas will help the HC?

 

[Dan4510]

make sure you get the car good and hot and that it immediately goes on the smog dyno. Refuse to just sit.

The catalytic converter needs to be hot to function correctly. Them letting it sit for an hour and then idling it is not enough.

Dan

 

[oilyriser]

Sine there's still some oxygen left in the exhaust, you might want to wrap your exhaust pipe with glass fiber insulation between the engine and the catalytic converter.

My car has some white fiber insulation under the
exhaust heat shield right from the factory.

Chemical reactions work much faster when you raise the temperature even a small amount like 25 degrees.

 

[Drew99GT]

Sounds like you got stuck with a California emmisions equipped 4afe. All others don't even have EGR.

Do you by chance have a repair manual for your Prizm? I have a 94 Corolla with a 7afe, and my engine has no EGR at all. However, it says in my Haynes manual that ALL 7afes have EGR

Regardless, it passed emmisions with flying colors. Maybe you should just rip all your smog stuff off!!!

 

[Drew99GT]

One other thing: fuel system. Seems like you may be slightly lean. Try changing the fuel filter, but be warned, Toyota overtightened the fittings on factory filters which crushed the acorn seal on the inlet fitting, so you may need a new fuel line if yours won't seal. Ask me how I know

Also, BG in can fuel injection cleaner that you hook directly to fuel rail. May also want to take the intake manifold off and clean it out. It's so easy to do on these engines that a child could do it, and it makes a HUGE difference, especially on EGR equipped engines.

[ February 08, 2004, 07:04 PM: Message edited by: Drew99GT ]

 

[tadaima]

Well I got the EGR cleaned out and NOX ran a lot better on the second test.

Wrapping the Exhaust path seems like a fun idea but I guess I should really find someone that will do that DYNO ASAP, seems to be a problem around here.

I'll try cleaning the intake and see how much that helps.

One thing I notice is that when my dad failed smog and got a new CAT, he started shooting out water from his muffler. I believe this is a good sign of a cat effectively doing its job since a general 2 way cat converts HC and CO to H20 and C02.

As for this 4afe engine, I dont really see much vapors in the morning.

If I do decide to get a new CAT what guarentee that this will reduce the HC by 26ppm?

 

[tadaima]

Yea i do have the repair manual for this car.

The fuel filter was changed probably 1.5yrs ago about 10K, don't thing that is bad yet.

 

[oilyriser]

I wish they would put a little vent ahead of the cat, so you could plug in a gas analyzer and see what's really coming out of the engine. Your engine might be running really lean and misfiring, and the cat could be hiding it as best as it can.

Someone with the time to do the calculations could look at those numbers, and see if there is exactly enough oxygen there to totally consume the HC and CO. If the cat is weak, but the engine is keeping close to stoichiometric, the nubmers would show it. If you still have oxygen left over after the reactions are complete, it means that the O2 sensor might be weak, causing the engine to run lean.

 

[tadaima]

I have a reading of 0.4 for O2, not quite sure if that's a surplus of oxygen.

Though for CO2%, I heard 14% is a good average number.

 

[tadaima]

Could the high amount of NOX running through the CAT poisen it?

Apparently I guess this car has been pushing out about 2300ppm of NOX at 15mph.

 

[rpn453]

Try running some ethanol blend gas for the next test, if you have it in your area. I've heard it really helps.

 

[tadaima]

Well most new gases in CA are ethanol based I believe.

Though finding additional straight dry gas "ethanol" seems to be hard.

 

[oilyriser]

Those O2 sensors can be checked using a voltmeter while the engine idles. If it's responding too slowly, the engine will swing further towards rich and lean as the O2 sensor switches on and off. Both ways will cause pollution to go up. A new sensor will respond quickly, and the engine will spend more time close to stoichiometric.

 

[jason07-1zzfe]

Sat for an hour? Or idled? Either way it is not good. I'd guarantee that's why the HC is high. Cats do not work unless they are hot and on older cars that do not have cat close to manifold, they take a while to heat up.
That they idle it and "kinda run it" before the test doesn't mean anything. It needs at least 15-20min of driving to make sure everything is hot. Run it hard to get it good and toasty. And I wouldn't sit around for more than a few min. Keep it running while you wait. Rev the engine high for a minute every few min to keep cat hot if you have to wait. but 1 hour? forget it...Go when you don't have to wait and you will pass.

 

[c502cid]

As long as were throwing things out, use up that premium and put regular gas back in. Way different burn rates.

 

[rpn453]

quote:

---

Originally posted by c502cid:
As long as were throwing things out, use up that premium and put regular gas back in. Way different burn rates.

---

I never even noticed that. Definitely use 87 octane on the next one. Your car wasn't designed for the premium.

 

[tadaima]

Yea I definately will use 87 next time, well I figure 91 would give it a better change of lowering the NOX, which it probably did, but made more HC, since a higher octane makes the flash point higher.

Well the tech said it sits around till the car before starts its test, so I assume within the hour wait, the car sits and cools for 45min and then runs 15min at idle.

I do agree..either way its bad...so I will really try to find a place that does it right away somehow.

We'll see after this weekend, I will have it run on Monday if the local shop is open, if not tuesdays.

 

[tadaima]

Well with the gas switched back to 87, changed the spark plug (even though the old ones had only 1K on them) and ran the car for lik 30min freeway, got to the smog place and it only idled for wait [10-15min], the HC at 25mph went from 131 down to 120, still off 105 was the limit..dang it

 

[Whimsey]

As oilyriser said previously get your O2 sensors checked out. How many miles on the car? Some O2 sensors will last a long time and some don't. But before you spend big$$$$ for a cat check the O2's. Even if you replace the cat and it passes but your O2's are faulty, you're just going to kill the new expensive cat in several months. What year car is this and is there a CEL or SES light on. Did you check for possible trouble codes stored in the computer?

Whimsey