hi all, new here,

91 rs, took it to be inspected, failed with class..
heres what i got: unburned hydrocarbon levels are roughly 1.5 times the limit in MA, and im getting CO levels that are something like 1% over the limit.. but i shouldn't be even close to that line anyway..

i broke out an old chem textbook and figured out that both of these levels are high because i'm not getting enough oxygen into the combustion reaction.. meaning not enough air i guess.. so now what? could the solution be as easy as a clogged air filter? was going to check it an hour ago, but can't find a 10mm socket.

also, engine misfires occasionally, hardly noticably, at idle. this is most likely do to the spark wires having too much resistance, i think.. and this could have a bearing on the emissions, but im not so sure how it ties into the whole lack-of-oxygen problem.

ideas? solutions? thanks

-ian

 

Ok, CO is your rich indiactor, the richer the mixture, the higher the level. So yes, in essence, CO is caused by not enough air to mix with the amount of fuel that you have.

Clogged air filters could cause the problem, but it's very uncommon. Good thing to check anyway though. Post the numbers, they help me out a lot(I'm a Smog Tech in CA, so I've seen my fair share of emissions reports). HC can be caused by either elevated CO levels, misfires, or a combination of both.

The first thing I would do, especially if you know that you have a mis, is a complete tune-up. Search for the TomP Tune-up here on the V6 board, it's a great start.

After the tune-up is done, you'll want to try addressing the CO problem. Trying to figure out emissions problems is a difficult thing to do without specialized test equipment, but I'll try to give you as much info as possible so you can do as much as you can by yourself.

There's another thread on this board that's been posted to recently regarding a car that is failing for CO at 2500RPM on a California test. I gave a lot of info there, so a search for that thread might be a good place to start.

Here's the link: https://www.thirdgen.org/forums/v6/3...ch-exaust.html

Welcome to the boards and good luck.
Jeff

 

here are the numbers:
HC grams/mile - 1.76.... limit is 1.2
CO grams/mile - 20.03.... limit is 20.00 (no cigar on this one)
NOx, fine, 1.39 gpm vs limit of 2.5gpm
CO2, fine, unlimited anyway

thanks for the help

 

you're not failing by much. Barley outside the limits. When was the last time the engine had a complete ignition set and O2 sensor? That's where I would start. Go read the thread that I liked to before, there's a trick in there that I write about to tell you if you're entering closed loop and if the O2 sensor is actaully functioning properly.

In your case, if the light stays off longer than on, you know that you have to replace the O2 sensor because it's not telling the computer the truth.

We know that you're running rich, so if the light is off longer, then the O2 is reporting lean and the computer is dumping in fuel, causing the rich condition.

I would definitly start with the Ignition system and O2. Since you don't have the actual test equipment, you'll just have to replace parts until you pass, but this gives you the best chance. Play the odds, you know.