failed emission test, what to do first?

[chromatin]

91 pontiac grand am, 2.3L quad4. Car runs fine. Might be a very little bit of roughness at idle. Drove ~ 10 miles before test. Outside Temp 63 F. coolant Temp at 160-220 F after driving for 2 miles maybe. Here is the result.

idle 2500 limits
HC PPM 375 161 220
co% 0.01 1.55 1.2
co2% 12.6 12.2
RPM 920 2517

Running rich? What to do first? Thank you very much!

[tdewitt27]

check eng light on? have you done a tune up? have you check oxygen sensor? check plugs? and wires? check ecu?

[chromatin]

No light.

Plugs and air filter are ~1.5 years and 10k miles old. Oil is brand new. Fuel filter was changed 2 years ago in a garage. All other fluids are almost new (related?).

They only visually inspect the O2 sensor here and it passed. So don't know how good it is actually now.

The car was bought 2 years ago. It failed emission twice just two days before the title was transfered. But I didn't know that until several months ago when checking its carfax history just for fun. Don't know what the girl did to it to get it passed.

Any other thoughts?

[alegar001]

I more then likely is the O2 sensor. Memory servine the one before the cat is the one use to measure out O2 content and the one behind is for the SES light as it measures the cats effect on your exhaust, You should probly replace them ore atleast the one before the cat. Its one of those parts that you can't really tell by its looks.

Also try some octaine booster it makes the engine run a little hotter and causes the fuel to burn more efficiantly. Which causes less emmisions as more of the fuel gets burnt. Should also take care of any nasty that is lingering around in the fuel system.

Peace ;)

[chromatin]

OK, poured a bottle of Guaranteed to pass (one type of fuel injector cleaner) into it. Will replace the air filter tomorrow since the car saw some unpaved, dusty roads twice. Let's see later. Hope it works.

Honestly, since the CO% is just a little bit high @2500 rpm and HC only less than twice the limit @ idle, I guess the cat or O2 sensor are probably fine. Otherwise, I would expect the numbers would be way off and should be off at both idle and 2500 rpm. Educate me if worng though. Now I am preparing to touch them if it fails after the g2p but not now.

BTW, what do you think idle @ 920? High for this car?

[alegar001]

It so so, mine idls at about 900 as well but i have seen some new cars that idle at about 500 rpms. Personally i think its ok

Could be that the O2 sesor is not readin accurate. Which would give false readins to the pcm and throwing things off a bit. If you pas tomorrow then I wouldn't worry to much about it. But if you don't then atleast you have part of an idea where to start.

Peace :D

[92CamaroRS]

Originally posted by chromatin
91 pontiac grand am, 2.3L quad4. Car runs fine. Might be a very little bit of roughness at idle. Drove ~ 10 miles before test. Outside Temp 63 F. coolant Temp at 160-220 F after driving for 2 miles maybe. Here is the result.

idle 2500 limits
HC PPM 375 161 220
co% 0.01 1.55 1.2
co2% 12.6 12.2
RPM 920 2517

Running rich? What to do first? Thank you very much!

take the car for a longer drive, 10 miles is not enough to efectivly heat up the catylitic converter.


If its the original Cat, i would say its probably fairly worn out.

[Conley]

Move to Florida!

[chromatin]

Oh, yes, I am going to move next summer, but probably not FL. Also, this year (actually only 3 months left) is the last year Colorado will do emission test. It sucks, especially for an old car!

[chromatin]

OK, passed! Here are the numbers:

idle 2500 limits
HC PPM 7 18 220
CO% 0 0.01 1.2
CO2% 14 14.4
RPM 451 2466

I think that guy put the RPM probe in the wrong place. Idle RPM is way too low, only about a half of the right number. He did put it in the right place later and showed the right 910 rpm.

The reason?

New air filter? probably not. But I did find my old filter didn't totally seal the housing. The car breathed dusty air for a year! D***! Forgot which brand I bought last time and D*** GM, quite difficult to check the air filter!

g2p? Maybe. Obviously, the engine is burning better.

O2 sensor and Cat? NO.

But I think last time neither o2 sensor nor cat was in their working temperature. Thus The engine ran in default condition and failed!