I'm looking for any advice on where to look for the cause of my Emission Test fail. (Ontario)
1997 2.2 with just over 200,000km.

Curb idle test is well within limits on all readings.

Driving test fails CO%. The HC ppm and the NO ppm are within limit.

The car is running on an oil and filter change only 2 weeks ago along with new air filter.
I installed a new O2 sensor, took it for a really good run on the freeway just prior to a retest and on 1st retest now the idle results are even better, but the CO% is slightly worse failing and now also the HC is right at the limit.

Any thoughts as to where to look next are appreciated. Even better if any recalls having a car fail with similar results and remembers what the fix was.

TIA
Mike

Heya Mike, Another fellow Canadian here, What kind of gas did you use? I always add $15-$20 in chevron 92 octane, as well a good run on the hwy 120 kph for about 5 mins or so. Have you done a complete tune up, Plugs / wires?. Could have a problem with youre Catylic converter, Its a common problem, I know Vancouver B.C. aircare is sometimes really picky, I drove my 80 camaro with dual exhaust, with glass packs No CATS, Guy told me my car could fail, I was pretty sure it would pass and it did, Like you listed : oil and filter change only 2 weeks ago along with new air filter, new O2 sensor, Took it for a good run on the hwy, I believe you CAT needs replacing. After that I would get some good chevron gas 92 octane, as well as a good run on the hwy, It should pass with no problems.


Good Luck

Keep us updated.

I was thinking CAT next, but of course that is not cheap. I did put $10 of Sunoco Ultra 94 into an empty tank before the test. I also did run it long and hard at 100-120 for 30-45 minutes just prior to the 2nd test. Checked and bumped tire pressures to the high side. I did not do plugs and wires yet this time as they are less than 12 months old and are not cheepie parts. I used Bosch wires and AC delco plugs, as I have heard all the stories about ignition on the Sunfires, as well as plug woes when trying the platinums.

I'll be waiting until next week until I work on it again. Any other thoughts on this would be appreciated before I spend the $$$ on a CAT.

Mike, quite often only one spark plug in a set is weak...

If you pull all 4 you may find there is a defective plug

with dark deposits...

>>>'I used Bosch wires and AC delco plugs, as I have heard all the stories about ignition on the Sunfires, as well as plug woes when trying the platinums.'<<<

ahem what stories? recently, especially when the car is sitting overnight, i noticed that it takes quite a bit of effort to start it. at first i thought maybe it's the fuel filter or something minor. i'm using bosch platinums that i installed in the summer and i was thinking maybe these are the problem.

btw with regards to your car failing to pass emissions, i had a ciera that refused to pass emissions even though i replaced the cat converter. the o2 sensor was fine. turned out it was an internal coolant leak because the intake manifold went bye bye, by the time i realized that i said @!#$ it. the car was really rusty anyway with 300k so i scrapped it. but believe it or not never had any major engine problems with that car, just routine maintenance. ahh long live the 3300.

Basically, CO and HC are poor fuel burning. HC is unburned fuel, CO is incomplete burn. NO is too hot a burn, btw. Cat is a possibility, the OE ones are crap. Coil packs can go south, to. Try a SeaFoam treatment for sure, but have the other parts checked.

Thanks for input all. I'll be getting back to working on this problem tomorrow.

One more thought for input. Since the E Test fail, I have discovered that when the gas tank if filled to the very top, there is a fuel leak near the back. I have not had time to pinpoint the reason yet, but suspect either the tank itself on or near the top side, or the filler tube/connections, etc. As this is part of the sealed fuel system, EVAP and the like, is it likely an air leak at the tank (when the tank is not full - as it was during the 2 previous e-tests) would result in CO failing high, and HO also being high, only during the drive test, while being OK at idle?

Obviously I will be fixing the leak before another test run, but I am wondering if this alone could be sufficient to cause the failure, and is it worth paying for a retest before going any further? Or is it likely that it will just fail again as this is not likely to cause high CO and HO.

I also note that on the list of common causes for E-test fail, defective EVAP/purge is on the list for hi CO, but not for hi CO. And also that a bad EVAP system does normally set a CEL code. This car did have a CEL several months ago for EVAP high leak rate, that I fixed after locating a split in the vacuum supply tube off the manifold to the purge solenoid. EVAP now tests good with no CEL.

BTW the car runs great and has very good MPG.

Tired the plugs - no joy.
Final fix was the CAT.

Thanks to all who input.