I actually installed a cat when I went to the emissions. The cat I got welded on there, however, was in dubious shape. I am in Illinois, and it's the IM240 test (with the dyno and everything). The testing results were not cool, the ghettoness has not prevailed. Well, here's the graph I hope someone will help me out with this, since I am leaving the country in three weeks and by the time I am back, my emissions testing notice will expire!!

I've had some problems with my emission the last two years also. Here are some possible solutions:

HC - High Hydro Carbons (Raw Unburned Fuel)
Incorrect Timing
Tune Up (plug wires, distr. Cap, rotor button, etc…)
Incorrect Idle (sensors)
Vacuum Leak
Air/Fuel Mixture (O2 sensors)
Throttle Body
Injector Problem
Carburetor Adjustment
Excessively Dirty Oil


CO - High Carbon Monoxide (Improper Fuel Mixture)
Dirty Air Filter
PCV System
Air/Fuel Mixture (oxygen sensor)
Carburetor Adjustment
Mechanical Condition (worn engine)
Excessively Dirty Oil
Mixture Control Solenoid


Hope these help you out. Good luck.

Thanks Tim!

OK, here's a couple of more details that could make troubleshooting more specific.

As said in my signature, I ported the throttle body and the thing runs open air. So in theory it should get plenty of air and I actually had a feeling that on open highway at higher speeds the engine runs almost lean.

However, he stupid fan that they put during emissions in no way emulates real-world conditions though -- I have a fiberglass cowl hood and when that air pressure gets significant my hood starts visibly vibrating...

So I am confused about high HCs.. I had leaky injectors before and replaced them. I am going to check them again. My car idles nice at ~600 RPM.
My mileage is good (~25 mpg highway, ~18-20 city)

And then look at the huge amounts of CO+CO2, is the cat I borrowed scrap? But does that explain the HC levels, does a cat do anything to kill the hydrocarbons?

Man, I hate this, my car has 151K miles on it, it's a miracle it runs, how do they expect it to pass this kind of emissions?

My sparks are due for a change, and I think I need to change the oil too.. how much will that affect the results?

I'll check the timing but it feels allright, I guess because the car idles so smoothly...

Oh yeah, the PCV valve is new and I replaced the EGR valve with a used newer one (the diaphragm is not as stiff)..

I feel like I am talking to myself, but here is some more info that might be helpful...

The IM240 requirements for model years 1986-1993 are
CO: 15.0 HC: 0.80 NOx: 2.00

My results are
CO: 55.1 HC: 1.50 NOx: 1.70

So, NOx is below crazy levels, meaning that EGR stuff probably works
Now, the insanely high CO and quite steep HC is what's worrying me.

On http://www.colostate.edu/depts/NCVEC...erters/az.html
I found out some calculated normal enigne-out CO (before it hits the cat).

My weight is 3403 so I should be getting between 16.0 - 17.0 engine out CO readings and the cat should make those really really low afterwards.

However my CO is way out there, above what it should be for my engine, and my HC is high.
The answer is obvious: I am running rich.

But how is that possible??
What worries me the most is the irregular spikes in the HC chart. Something's really wrong...

Is it just sparks? I am definitely changing those and changing the oil.. Maybe that brand new distributor cap that I got for free might be of some use now... checking the timing?

Anyone been here before? Am i talking ?

Any comments are really appreciated, I have about 2 weeks to work on this..

replace "dubious" cat with "new, working" cat.
set the timing correctly
give the car a tune up (plug wires, plugs)
repost new test results

well, replacing the cat is a bit on the costly side.. They have those $20 emissions-test thing that doesn't go on your record. (voluntary testing), so I'll try to do everything else, take a voluntary test, and if I don't pass, change the cat too.

The major problem i see here is that CO readouts are well above what the engine is supposed to produce without a cat (it should produce some 16-17 gpm), so I can't blame the cat right away.

The NO2 levels were below mandated levels and there was a substantial CO2 output, indicating that there was conversion going on...

So, OK, I'll change oil, spark plugs and the wires (if the wires are not too expensive), I'll check the distributor and change the cap if necessary (hopefully the rotor is OK), check the injectors (again), and the timing and see where that takes me...

Nox are produced when normally inert nitrogen combines through combustion heat with oxygen. The EGR feeds inert exhaust gasses back into the system to lower combustion temps to around 5000 degrees. Without EGR your looking at 7000+ degrees and around 7000 nitrogen can combine with oxygen. The HC levels are related to combustion efficiency where an incomplete reaction produces CO and hydrocarbons are essentially unburnt fuel or octanes broken into lower hydrocarbons by partial combustion ie septanes, hexanes, pentanes, butanes, propanes, methanes etc. A proper functioning cat catalyzes those hydrocarbons by basically breaking them down further till we end up with H2O or CO2 which is the goal. This is done with high cat temperatures, so if you have a themal gun, get at a radio shack, you should see when working the cat will skyrocket in temp forgot the numbers but there's the temp of exhaust gasses in the y-pipe and headers and then then the cat when the reaction occurs which is significantly higher. Its what's described at a fired up cat. Now there are 2 ways to promote this. Assuming you have a good cat, simply insulating the cat, heat shield to reflect the heat back to cat should get it hot enough to fire. The prob is you depend on a good supply of O2 in the exhaust gasses to complete the combustion so even if it did fire up, no guarantee that there's enough O2 to use and your HC will go down but CO will go up or CO goes down and HC goes up. It usually tends to be CO going down by HC skyrocketing. Now another system is an AIR system which feeds air into the cat, this relies on exhaust gasses being relatively high temp. So the conditions for an air system are, CAT does fire, exhaust temp is high, HC is high because O2 is lacking. I think though you'd rather get the engine tuned up first to increase combustion efficiency. high HC and CO means low combustion efficiency so a tune, new more efficient performance wires and distributor rotor and cap, spark plugs, air filter (or if it's K&N clean it). This will all increase combustion efficiency and thus drop BOTH HC and CO numbers. I actually got mine to pass with a standard filter lol. Before an emissions test you should always do a tune up. Once you know your engine is at its peak efficiency, then worry about the cat. You got a used cat AND your forcing it to do a lot of the work. You want combustion in the engine making more power, not in the cat making just heat. With that said and done I got mine to half those standard levels. On top of it I make more power than in stock.

Marin, here are my two problems from my last couple years of testing:

2001: MY HC's and NOx's were high. I was around 144,000 miles. My thinking, was for the most part, along with yours. I changed the oil, new plugs and wires, new cap and button, PCV, air filter, breather filter, and EGR valve. I went back for a retest thinking I had it beat and my HC's actually went up. I went back hooked up my scanner to check for codes and found none. My next thought was the cat. I had it changed (not cheap $400), went for my third test and it PASSED. All my readings dropped significantly with just a cat change.


2002: HC's and NOx's were high. These readings were high again this year but not near as high. HC's were just fractionally high while the NOx's were too high. I had sat in traffic on the interstate for half an hour with the car 220* and then had the car tested anyway. It of course failed. I went back changed out the 160* thermostat for a new one and the car tested first thing in the morning with the advance on the distributor unplugged and the car relatively cool and once again it passed easily.


My advice would be to do the tune up items or anything you can do yourself. Check the ECM for any codes (O2 senor?) and check for vacuum leaks. A cat change may seriously have to be considered though. Let me know how you come out. Good luck.

I don't know about everyone else, but around here a new cat won't even set you back $100. My local performance muffler shop (muffler tech here in Sacramento) installs any cat for $20, and they sell most of the catco's for $60 each. So for around $100 you will make a VERY big difference in your emissions - cat is worth it's weight in gold. (but not $400, ouch, that seems like a rip-off???)
by avoiding replacing the cat you are avoiding the single most helpful part of the entire emissions system.

Okie, 91L98Z28 to make myself clear -- I totally agree with what you say and in the end I am going to replace the cat. But I want to check other things first, since my ghettocamaro has so many miles on it and until I pull the sparks out, I wont really know if it's just the cat, especially because the CO is way above what (according to that link I posted) "his ghettoness" is supposed to be with !cat.

Thanks guys your stuff really helped me beginning to figure out what's wrong.. (Slade1, that was very detailed and helpful; TimRS, thanks for the hints)

===

Preliminary check:

Fuel Injector spray = flawless, real nice
Code Scan:
Code 32 ---> EGR system fault

The NOx's are low (passing, but not that low), is the problem really in EGR?
Can that have *anything* to do with HC spikes and ultrahigh CO?

Still seems like ignition trouble to me.. probably foul sparks... comments?

If I remember correctly, an EGR fault is indicated when the diagnostic vacuum sensor/switch doesn't "sense" vacuum when the computer thinks it should. This either means (A) defective diagnostic switch, or (B) vacuum leak, or (C) defective EGR solenoid. If you have a vacuum leak in the EGR system, this could play double havoc on your emissions, as not only do you have the vacuum leak to lean the mixture, but also a non-functional EGR.
You may also wish to check other areas...Is the car getting up to proper operating temp (195F+?) If the engine never hits operating temp, then the computer will command it to run rich. 160F thermostat is a no-no. If you have a buddy with diacom or the craig moates software, a quick scan of the car prior to being started, and after fully warming up, will point out any defective temp sensors which could signifigantly affect the fuel ratio the computer is trying to spray.
good luck!

OK, I think it's not (A) because the SES light comes on only occasionally on highway driving. So, either (B) or (C)...

You got me thinking with that coolant info.

I have to change that coolant temp sensor...
This is one of the reasons I did the Manual Fan Override. My stat is OK, but my fan wouldn't turn on or it would turn on way too late, when the engine is heavily overheating...

I looked at my ECMs dissasembly (from diy-efi) and looking at how BPW is calculated with respect to coolant temp. The BPW can be changed significantly depending on what the reported coolant temp. is. It explains how my idle rarely drops below 700 RPM. And I think something like 550 is desired.

"cat is worth it's weight in gold."
considering that it's platinum doing the conversions... yes, this statement in mostly correct.

I'd like to say what first hit my mind when I saw the CO chart:
"dude, you could kill someone with that car!"
I know that's quite obvious...

to be frankly honest, if you take good care of your engine, a cat is supposed to last almost indefinitely.... but we all know that any engine that had 150,000 miles on it hasn't exactly had 50 oil changes and stuff like that.... 10 different sets of sparks is pushing it...

btw, my eclipse and voyager are pushing 180,000 and have never failed an emissions to date.... not even come close... not that this relates to the fine machines that f-bodies are, but my camaro has had TONS of abuse (try several years of sittin in a parking lot during the gulf war) and I even believe it to have a gutted cat.
I ran my special mixes into my oil and gas and it passed with flying colors.
special mixes= slick 50, engine restore, octane boost, fuel system cleaner.
also try that "pass emissions guaranteed" stuff...

okay I'll put down the pipe now.

I haven't tried this, and I don't know how it would work with an efi motor, but a nunber of members on the chevelle board I'm a member of swear they can pass any sniffer test by running gas mixed with denatured alcohol - a 5:1 ratio. SC

I PASSED!!!!

List of things I did (for future reference) :

1) Changed the sparks (each had at least 80K)
My idle dropped by ~100 RPM in idle and drive...

2) Changed the aircleaner element
Put the K&N lifetime warranty one in... The car became a little more responsive..

3) Changed the oil, changed the oil filter (Valvoline Maxlife)

4) Put Dynomax Walker Direct Fit cat in ($110)
Noticed my car couldn't peel the tires anymore... either my Kumhos (245/50/ZR16) broke in or (b) the cat is restrictive. I think (b)... that cat is going to be replaced by my 'flow enhanced' version

5) Begged the welding guy to completely seal my AIR pipe so it doesn't leak anywhere... (priceless)

How well did I do?

I passed in 31 seconds... I passed so fast I thought there was something wrong during the test

My HC levels were 6 times under the level required for composite fast pass and my CO levels were 2 times under the required level for fast pass.

No NOx, CO2 level (measures cat efficiency) was 1.00

In Illinois they run IM240 test under the newest, strictest standards for cars past 1988... mine is 1992, BTW...

Thanks everyone for the suggestions, I am free until 2004!!!




BTW, putting isopropyl achohol and various enhancers usually doesn't work on EFI.. TRAXION tried it and it still didn't help enough to pass.

man im glad i dont have emmissions here...im sure my "flowenhanced" pipe, hooker headers without air, smog pump delete would fail so miserably they would catch the car on fire and the EPA would put me under the jail actually my car would probably pass very easily with a cat on since it runs perfect and has a nice tune up. plugs are fouling fast from bad valve seals tho.

When I got my car, it failed HC emissions mightily. Of course, I later found that this was due to a previous owner who thought that 'tune-up' was something you do to a guitar. New plugs, new aircleaner, new PCV valve and filter, timing-reset (it hadn't been set in so long that the distributor bolt was stuck, I busted some socket-wrench adapters getting it loose) and an oil change later, I passed (Wisconsin used a dyno-based test, and just adopted NOx emissions standards recently. Very similar test)., and the car ran better too...

As for the cat, I just got done changing mine (the stuff inside cracked and plugged my exhaust, so it was either run slower than a 3-cyl Metro, or change the cat), so I can put this in for you...

Changing the cat requires (a) a new cat (Random Technology sells them for $250-300 or so if you want a nice 'high performance, non-restrictive' one, but you can get a stock replacement from Walker for less than $150), (b) a dremel (so you can cut the old one off your front exhaust pipe), (c) diamond dremel blades (sears, $10 or so) and (c) some time. Then just cut away half of the cat's slip-on pipe (which goes over the Y-pipe) or whatever you have to do to break the welds, and take it off.

Of course, my cat wasn't welded on (normally it's just a slip joint on the front side, and a flange on the back), just rusted on (hence the dremel, and the cut-half-the-outer-pipe off)...

Alot of people here seem to reccommend that you upgrade your exhaust to 3-inch (or at least use a 3-inch cat with adapters, so you can easily upgrade later) when you do this, but that's another story... I kept the stock exhaust (mostly because I just put on a new intermediate pipe last year (prior to coming to this board), and got an all-in-one stock-size unit instead of a proper catback system (Silly me, I know)...

Also, don't weld cats... Use U-clamps.... And drive around with your new cat on for a month or so before you get tested - a BRAND NEW cat will FAIL emissions because it isn't broken in yet...

Finally, your AIR injection tube will be a pain to de-tach. I had to cut mine off, and I still haven't figured out how to rig it back up yet (thinking metal flex-tube)... And yes, you can legally replace your own cat on a 92 (the rule is 50,000 miles or 5yrs)...

im with you. I can get a new cat installed at the local muffler shop for 110 dollars.