I have a 92 vette Lt1, I went for a smog and failed. My HC numbers were 148 at 15mph. The limit is 77. At 25 mph it was 139. The limit is 59. My CO numbers were 1.19, 0.50 was the limit and 1.22 with a limit of 0.49 My NO numbers were 1038 with a limit of 541 and 1026 with a limit of 498. So with these numbers I went out and got brand new CAT's and O2 sensors and went for a re-test, not only did I fail but my numbers went up and the car was classified as a gross polluter. DTC's read 43 and 65...somebody help me please. I'm on the verge of selling my beloved Vette.

 

Here is a little in depth reading that may help....

Following are a few general facts and tips to keep in mind when using the gas analyzer:
1) High Carbon Monoxide (CO) readings usually indicate a fuel mixture richer than ideal (rich mixture - air fuel ratio below 14.7). In general CO is an indicator of combustion efficiency. The amount of CO in a vehicle’s exhaust is directly related to its air-fuel ratio. High CO levels result from inadequate O2 supply needed for complete combustion. This is caused by a too rich mixture - too much fuel or not enough air (AFR readings below the optimal 14.7, Lambda below 1.0). Circumstances that can lead to high CO emissions:
* Low idle speed
* Improper float settings in carbureted vehicles
* Dirty or restricted air filters
*Excessively dirty or contaminated oil
*Saturated charcoal canister
*Non-functioning PCV valve system
*Improper operation of the fuel delivery system
*Improperly functioning thermactor system
*Catalytic converter intervention and CO concentrations
High CO readings at the tailpipe are a clear indication that there is a problem in at least one part of the system, but a CO reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. Low range CO readings are possible, and not uncommon, from a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter CO levels will be masked by the catalytic converter and the potential for an CO problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.
NOTE: Great caution must always be exercised when dealing with CO. Concentrations of less than one percent can be lethal. Testing should always be done in a well ventilated area.
2) Normal CO readings. If the combustion process is succeeding at or near the stoichiometric point (AFR equals 14.7, Lambda equals 1.0), CO levels during an idle test will typically measure less than 2%.
3) Low CO readings. There is, effectively, no reading for CO that can be characterized as too low or "below optimal". CO concentrations will appear "normal" even in a lean burning environment, where AFR is above 14.7 (Lambda is above 1.0).
4) High hydrocarbon (HC) readings usually indicate excessive unburned fuel caused by a lack of ignition or by incomplete combustion. Concentrations are measured in parts per million (PPM). Common causes include a faulty ignition system, vacuum leaks, and fuel mixture problems. Circumstances that can lead to a high HC emissions are:
* Incomplete combustion due to fouled spark plugs.
* Improper timing or dwell
* Damaged ignition wires
* Poor compression
* Vacuum leak
* Ineffective or faulty air management system (ECM control of air/fuel ratios)
* Catalytic converter intervention and HC concentrations
High HC readings at the tailpipe are a clear indication that there is a problem in at least one part of the system, but an HC reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. HC readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter HC levels will be masked by the catalytic converter and the potential for an HC problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.
5) Oxygen (O2) readings. Oxygen, measured as a percentage of the exhaust volume, reflects the amount of gas remaining in the exhaust sample after the combustion process has taken place. Ambient O2 readings should be about 20%, reflecting the natural amount oxygen found in the air. The ideal range for vehicles without a secondary air injection system is less than 1.5%. If there is an air injection system, O2 levels will typically fall n the range of 3% to 4%. Pinching off the air hose of a vehicle equipped with air injection should produce O2 levels similar to those found for vehicles without air injection.
6) High oxygen (O2) readings indicate too lean an air-fuel ratio (AFR higher than 14.7, Lambda greater than 1.0). Circumstances that can lead to high O2 emissions are:
* Lean fuel mixture (AFR above 14.7)
* Vacuum leaks
* Ignition related problems causing misfires.
7) Low O2 indicates a rich fuel mixture (AFR below 14.7, Lambda below 1.0).
8) High carbon dioxide (CO2) readings indicate a nearly ideal air-fuel ratio and efficient combustion
9) Low carbon dioxide (CO2) readings indicate a fuel mixture either too rich or too lean, exhaust system leaks, or sample dilution.
10) Oxides of Nitrogen readings. Oxides of nitrogen (NOx), including nitric oxide (NO) and nitrous oxide (NO2), are formed if the combustion temperatures within the combustion chamber exceed some 2,500 degrees F. This can occur when the engine is under load. When excessive temperature conditions exist, the greatest amount of NOx is typically produced at the stoichiometric point (AFR 14.7 or Lambda of 1.0) as the engine is under a light load. If the combustion process within an engine is burning fuel at or near stoichiometric point, NOx levels on acceleration will typically read significantly higher than those measured at cruise and during deceleration. Typically, the NOx readings at idle will be 0 PPM.
11) High NOx Readings. Circumstances that can lead to abnormally high NOx emissions are:
* Malfunctioning EGR valve
* Lean fuel mixture (AFR above 14.7, Lambda above 1.0)
* Improper spark advance
* Thermostatic air heater stuck in the heated air position
* Missing or damaged cold air duct
* Combustion chamber deposits
* Malfunctioning catalytic converter
* Catalytic converter intervention and NOx concentrations
High NOx readings at the tailpipe are a clear indication that there is a problem in at least one part of the system, but an NOx reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. NOx readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter NOx levels will be masked by the catalytic converter and the potential for an NOx problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings.
12) Low NOx readings. There is, effectively, no reading for NOx that can be characterized as too low or below optimal. NOx is naturally 0 ppm at idle. NOx concentrations may appear normal even in a rich burning environment where the AFR is well below 14.7 (Lambda below 1.0).


PM me and I can give you possible temp solution.

John

 

Do you have any modifications? Anything that is bolted on that can be removed for testing?

 

I'd say change the spark plugs, wires, cap and rotor, air filter and oil and throw in some seafoam and techron and do a couple of high speed/rpm blasts. Are there any warning or check engine lights on?

 

When you replaced the cats and o2 sensors - how long did you drive it before the retest?
You need to disconnect the battery, turn on the headlights, turn off the head lights, reconnect the battery and drive it for a week. Include at least 50 highway miles so the EGR cycles a few times.

Wen you replaced parts the computer did not reset the historic levels and was compensating based on old data. it takes a while to get it working with the new parts.

What brand o2 sensors? Some folks have problems with the bosch, do a search.

If that still does not bring it in line and everything else is up to spec (no exhaust leaks, no vaccum leaks) then you need to datalog it and see if you can get someone to make you an emissions chip.

Good luck - emissions testing is one of the reasons my 92 is working its way to full race car status.

 

I didn't drive it for very long at all, took it home from the muffler shop, about 5 miles, then went to get smogged the following day.

 

I made all the above mentioned repairs prior to getting new cats, and yes, I'm getting codes 43 and 65....code 65 came after I got the cats done.

 

Hmmm alright, it should be running like new then!

Try doing what jaa1992 said, that might help.

For the 43 codes try this :

http://forums.corvetteforum.com/c4-t...e-43-help.html


and for the 65 I couldnt find anything...try searching the forum and maybe just try disconnecting the battery and going on a good HW cruise.

Edit: I did find the code 65 and it indicates a ruch running condition- When you changed the old 02 sensors out, the new ones are probably more sensative so they pick up a reading, thus giving a SES indication of the rich condition. Try the above, that should fix that. Code 43 on the other hand...check that out with that posting.

Also, Is your base timing set right?

Good luck

Will