348 Emission Test Fail

Those HC and CO numbers aren't that bad if your cats are no longer really working internally (or if they've have been punched out).

You really can't "lean it out" since the amount of fuel added during gently warm running is ultimately controlled by the O2 sensors (or should be -- wouldn't hurt to measure what's coming out voltage-wise from the O2 sensors to see if the control system is running closed-loop when warm). You really need to get the same HC and CO measurements of the exhaust gas entering the cat to determine if the problem is excessive fuel delivery or just dead cats.

If you move to CO you would probably "pass" (as the limits here are more like 1.2% CO and 200 ppm HC).

 

Adding 20 ohms to 403 would be a good first guess, but it's just that, a guess. Lean too far and you will get a lean misfire which will jump up your HC's and fail your test.

Pull your spark plugs, clean them, and gap them to less than .028" . This will help reduce misses...the real enemy of an emissions check.

You will also lean out the system by some small amount if you clean your air filter, or for a brief test only (gasp), run sans air filter momentarily (not recommended).

New O2 sensors will help, too. Change your oil. And if all of the above doesn't work, then you've got a structural problem somewhere such as failed cats or bad spark plug wire/coil/MAF, etc.

Keep in mind, though, that the HC/CO/NO curve is pretty sensitive.

 

One question, what **gear** was your 348 in to be lugging around at 1921rpms for 25mph??

 

Aside from just plain guessing what you really need to know is as Steve said, the pre cat exhaust numbers. The post cat numbers are so manipulated, and by who knows what degree, by the catalytic converters they are of zero use in diagnosing a running problem. That is exactly why Ferrari on every road car provides a method for accessing pre cat gas for measurment.

Performing any adjustment or replacement of any parts prior to knowing that information will require divine guidence or dumb luck to actually get the car fixed.

 

Clearly you want the pre-cat exhaust numbers for a professional fix/tune.

But a couple of things need to also be considered: for one thing, most Fcar enthusiasts don't have access to those numbers, so a simple home fix turns into an ordeal of taking the car to a shop, leaving the car, sometimes for days, hassling with getting a ride back to the shop to pick up the car, etc...and then the enthusiast really hasn't learned how to handle the problem herself if it reappears.

What would be helpful would be a tip on how to get the pre-exhaust numbers at home, rather than a more generic statement that you simply need those numbers.

Another point, it's not all guessing. For instance, an emissions test performed in the wrong gear is going to have the engine lugging or over-revving, depending upon the wrong gear selected...both of which are going to be adverse to an emissions check.

And even when guessing, educated guesses can get in the correct ballpark (e.g. matching up both MAF's to have identical resistance settings at or near the factory pre-set 383 ohms mark).

 

If you are going to work on modern cars even at home an exhaust gas analyzer is very high on the list of equipment needed to keep yourself from working in the dark. I don't know about you but when someone tells me I need to know my temperature I know I need a thermometer, I don't need to be told. Also many shops would be happy to measure those numbers for you so you would not have to go to the trouble and expense of buying the equipment.

As far as testing the car in the wrong gear evidently you have no idea what a 21 century smog test consist of. They are performed on a dyno according to a very narrowly defined test cycle where the speeds and rpm ranges are selected for you and give you no latitude in gear selection.

Once again you are out of your element.

 

I've used an exhaust gas analzyer while my car was on a dyno, but the sensor-probe went into the tailpipe. The sensor probe was also substantially larger than the pre-cat ports in my exhaust.

So as a home enthusiast, I'd be stumped (big surprise, right) on how to get the pre-exhaust numbers with that exhaust gas analyzer. I'm probably not the only Fcar dillettante to be at that point, either...

...so a tip on how to obtain the pre-exhaust numbers would help a few 348 Brothers.

The tests vary from state to state, of course, with some states specifying a generic "2nd gear" at 25mph and other states having a chart to look up the appropriate gear for 25mph is said car.

The state of Washington says (http://apps.leg.wa.gov/WAC/default.aspx?cite=173-422-070):
"2. Vehicle Gear Selection: Vehicles with automatic transmissions use Drive (not Overdrive), vehicles with manual transmissions use second gear. Shift to the next higher gear if the engine speed exceeds 2500 revolutions per minute.

3. Vehicle Speed: Set vehicle speed at 25 miles per hour (mph) 1.5 ± mph."

All of the above brings up two legitimate questions:
1. was the 348 in 2nd gear and
2. is 2nd gear truly appropriate for testing emissions at 25mph in a 348?


And then you've got federal regulations that come into play, for instance, on background emissions.

http://a257.g.akamaitech.net/7/257/2422/12feb20041500/edocket.access.gpo.gov/cfr_2004/julqtr/40cfr86.096-8.htm

Which says "The demonstrated level of nonfuel background emissions may be subtracted from emission test results from certification vehicles..."

So if you are in a high smog area, your emission test results are supposed to subtract the ambient emission levels from your test results on your car.

But hey, I'm out of my element here, right?!

 

Forget the dry gas use 12 ounces of acetone per tankful, drive it around for a while and go for your test. Old pro's say it passes every time. Sh-h-h-u-sh! its a secret.

 

Sorry for your trouble but it is no surprise. Reread #5. There is no substitute for methodical diagnostics. My post and Steves post are the only 2 that can help. Everyone else was from fantasylandOf that there is "No Doubt".

 

Ahh..Good morning Brian. Hadn't read this post before. Other than post no. 2 & 5 another exersize in pissin' in the wind, I have understood that can be messy. LOL. This place cracks me up. Regards, Vern

 

I would disconnect the cats and have a look inside. I'm gonna guess that the ceramic is gone.

Last year when I had to get my car smogged I was failing by 0.1. Turned out that the right side cat was gone, completely burn out. The left side was fine though.

Since your MAFS readings are fine, I would just pull the cats and have a look inside.

 

Ernie's been through this before; he had a bad cat.

The Hyper-Flow cats will help emissions and performance, so that's a double win for you.

 

Before you spend the money, pull the cats and have a peek inside.