Failing Emmissions CO2

[bzettler83]

I have a buddy who has a 95 V6 and is failing emissions due to CO2. What do you recommend looking at first? Is there an easy fix, even a temp fix?

 

[RonJR]

I'm pretty sure you mean failing CO, not CO2. I don't know of any state that has a limit on CO2 emissions, certainly not for a '95 vehicle.

It would help a lot to post the actual numbers for all three emission components, HC, NOx, and CO. That gives insight into how the emissions system is working. Also, what has been the emissions history for this vehicle? Is this a problem you could have seen coming over the past few years of tests, or did it just pop up this time?

Generally high CO is due to over-rich fuel mixture and/or poor combustion (misfires, etc.) Make sure plugs and wires are good. Check for CEL and diag codes.

 

[Dropzone]

Pull the codes (your buddy would need to Jumper the diagnostic port since it isn't OBD2)

https://youtu.be/4st6Hf5-nJ4

 

[_ExpeditionMan]

Obviously I agree with others in this thread that your friend should pull the codes and fix whatever the issue is, after which I have a few suggestions to pass an emission inspection. I (allegedly) utilized these techniques after failing by a very slim margin and the results were great. As a side note my county requires dyno emission testing on OBD1 vehicles and finding a shop that does inspections and has a working dyno nearby is roughly equivalent to being stabbed repeatedly.

1) Drive your truck for a a decent amount of time before the inspection to get everything warmed up, including your catalytic converter. Everything runs better at operating temperature.

2) If you have the tools and the ability retard the timing slightly before the emission test.

My 4runner passed with flying colors on all of the administered tests. Also definitely pull those codes.

 

[RonJR]

Absolutely agree with having your vehicle completely warmed up before you show up at the emissions station. Cold cat converters and cold oxygen sensors don't work well at all.

So far I haven't had to mess with the timing. Colorado requires testing (on the dyno) every two years. Each time the '94 gets a little worse, but it still has quite a bit of margin. Next test is in 2018 - hopefully it will come through again.

 

[_ExpeditionMan]

Absolutely agree with having your vehicle completely warmed up before you show up at the emissions station. Cold cat converters and cold oxygen sensors don't work well at all.

So far I haven't had to mess with the timing. Colorado requires testing (on the dyno) every two years. Each time the '94 gets a little worse, but it still has quite a bit of margin. Next test is in 2018 - hopefully it will come through again.

Is it dyno testing for OBD1 vehicles only and are you exempted after 25 years? Here in Houston there are only about three shops near me to choose from and only one of them has a dyno which works more than half the time. I failed my most recent test by .01%. I kid you not, the tech looked at me and said he had never seen that in 15 years. I told him that was probably within the tolerance of his testing equipment, but he had to fail me anyway. Reduced the timing by 2 degrees and passed with TONS of room to spare.

 

[RonJR]

Colorado has eliminated the independent test stations, and set up state run emissions stations, with multiple dyno bays. The technicians can't do any adjustments, but they're pretty helpful with suggestions if you fail, and I've seen them repeat the dyno test a couple of times to make sure the vehicle was thoroughly warmed up, if it failed the first time. I like the system better than the old independent shop system, because it's very consistent and you know what you're dealing with.

Colorado also has a "drive-by" testing system. A couple of times/week they will set up roadside monitors on freeway on-ramps or on a steep hill, where the engine is loaded, and monitor your emissions. If you pass twice in a 2 week period they mail you a compliance certificate and you don't have to go to the test station. No consequences if you fail. The standards are tighter than at the actual dyno station, but the advantage is a CEL for a bad transmission solenoid, for example, won't cause a failure. They publish the times and locations of the roadside monitors on their website.

 

[_ExpeditionMan]

Colorado has eliminated the independent test stations, and set up state run emissions stations, with multiple dyno bays. The technicians can't do any adjustments, but they're pretty helpful with suggestions if you fail, and I've seen them repeat the dyno test a couple of times to make sure the vehicle was thoroughly warmed up, if it failed the first time. I like the system better than the old independent shop system, because it's very consistent and you know what you're dealing with.

Colorado also has a "drive-by" testing system. A couple of times/week they will set up roadside monitors on freeway on-ramps or on a steep hill, where the engine is loaded, and monitor your emissions. If you pass twice in a 2 week period they mail you a compliance certificate and you don't have to go to the test station. No consequences if you fail. The standards are tighter than at the actual dyno station, but the advantage is a CEL for a bad transmission solenoid, for example, won't cause a failure. They publish the times and locations of the roadside monitors on their website.

That drive by emissions testing is both interesting and concerning. How does it work if you fail? Is there any record of it or penalties? Also I would love to have a state run inspection shop where they are forced to maintain their dyno equipment. Feels a lot more like Texas is trying to force you out of an older car by making it more difficult to keep it certified.

 

[RonJR]

That drive by emissions testing is both interesting and concerning. How does it work if you fail? Is there any record of it or penalties? Also I would love to have a state run inspection shop where they are forced to maintain their dyno equipment. Feels a lot more like Texas is trying to force you out of an older car by making it more difficult to keep it certified.

At this point there is no negative consequence of failing the drive by test, other than you don't get a certificate in the mail. As I said, the drive by test has more stringent standards, because of greater uncertainty, so they can't really bust you for a failure. Just force you to go to a station when your emissions test is due.

I'm actually pretty pleased with how Colorado has implemented the whole process. Much better than the inconsistencies of the previous system.

I think Colorado goes back to 1975 for emissions testing. Before that model year, you're exempt. On older vehicles (pre OBDII), there is also a dollar limit of what you have to spend before giving up and getting an exemption.

 

[_ExpeditionMan]

At this point there is no negative consequence of failing the drive by test, other than you don't get a certificate in the mail. As I said, the drive by test has more stringent standards, because of greater uncertainty, so they can't really bust you for a failure. Just force you to go to a station when your emissions test is due.

I'm actually pretty pleased with how Colorado has implemented the whole process. Much better than the inconsistencies of the previous system.

I think Colorado goes back to 1975 for emissions testing. Before that model year, you're exempt. On older vehicles (pre OBDII), there is also a dollar limit of what you have to spend before giving up and getting an exemption.

All of that sounds really good, except for the 1975 model year! I wish Texas would take a few notes from Colorado and implement something similar.