Camalot .I am thinking about you , and i do hope you get this nice car up and out of the smog bracket . Let us know how you get on please.

Thanks,

Still don't know about old gas. I checked my records & my mileage over the last 2 1/2 years & its become apparent the gas in the tank now is half
2 1/2 yo gas.

I'm trying to deal with this now as it could be affecting the smog emissions.


All the other parts of the smog test except NO seem to indicate an engine running fine.
HC & CO are fine. Does this mean that the fuel is burning well? Wouldn't old bad fuel be more likely to mess with the HC & CO? Seems when fuel gets old its less volatile so not burned completely which would increase the HC & CO.

Would old gas act in a way that would be similar to a lean fuel condition if its not burning well?
Also says high engine temp cause hi NO. The engine does run hot but has a new behr radiator & thermostat.


I'm trying to cut out this step of finding someone to take out about 3/4 of my gas approx. 15 gallons if it's not needed.

Also if HC & CO levels are fine doesn't this mean the catalytic converter is working?

engine - Best Ways to Pass Emissions? - Motor Vehicle Maintenance & Repair Stack Exchange


Mosts emissions tests will check NOx, CO and HC. A very basic rundown:


•NOx - Oxides of nitrogen. This means the engine is running too hot (2500F +). This can be caused by poor cooling or fuel mixture is too lean. Modern vehicles also have an EGR system, which exists exclusively to reduce NOx. If the engine is running in the correct tempuratures, and NOx is high and everything else is normal, the EGR system is strongly suspect.

•CO - Carbon monoxide. CO exists when there is an incomplete combustion of the air/fuel mixture. This can be caused by restricted airflow (dirty air filter), or a sensor that is reporting the incorrect airflow (MAF/MAP, TPS), or a faulty O2 sensor.

•HC - Hydrocarbons. This is raw fuel, meaning the fuel didn't burn completely during combustion. This can be an ignition problem such as misfiring, or poor timing. Usually this will show up as a driveability problem.


http://www.smogtips.com/failed-high-NO-nitrous-oxide.cfm



What Causes High NO (NOx)?
Nitrous Oxide or NO is created when an engine's combustion chamber temperature reaches over 2500F. Vehicle manufacturers have designed several systems, which when working properly, lower nitrous oxide emissions. Below are common failures which may cause your car, truck, van, suv, or motorhome to produce high high nitrous oxide.

1. Lean Fuel Mixture - Lean fuel mixtures cause high NOx. A lean fuel mixture exists when less fuel then required is delivered to the combustion chambers or when more air then necessary is added to the fuel. In either case the lack of gasoline needed to cool the combustion chambers down is not present. Combustion temperatures increase causing high nitrous oxide emissions. A lean fuel condition may be due to a vacuum leak/s (possible) and/or defective fuel control components, such as the Air Flow Meter, Engine Coolant Temperature Sensor, and O2 sensors (new).

2. Defective EGR System - The Exhaust Gas Recirculation system is designed to reduce NO. The EGR system consists of an EGR valve, EGR pressure sensor, vacuum hoses, and one or more vacuum switching valves or solenoids. Later model vehicles may be equipped with electronically controlled EGR valves, which do not require vacuum lines or switching solenoids. Electronic EGR systems will have these components built in.

The EGR system's job is to re-route a small amount of exhaust gas back into the intake manifold to help reduce combustion chamber temperatures. As mentioned above NOx is created when combustion chamber temperatures reach above 2500F.

By recirculating exhaust gas back into the intake, a small amount of the air/fuel mixture is replaced with inert gas, reducing combustion temperatures.



3. Defective Catalytic Converter (CAT) Some vehicle manufactures have designed their cars to operate without EGR valves. Non-EGR equipped vehicles rely heavily on the Catalytic Converter to assist in the reduction of NO. These vehicles have tendencies to develop CAT problems sooner then those which are equipped. If you own a non-EGR equipped vehicle, and have failed the emissions test for high NOx, pay close attention to the Catalytic Converter.


4. High Engine Mileage - Over an engine's lifetime, carbon build-up develops in the engine's combustion chambers. The more miles on your engine, the more carbon build-up on the pistons, cylinder heads and valves. Carbon build-up decreases the available space for the air/fuel mixture to combust, and causes higher cylinder compression. High compression results in high temperatures and high NOx. Keep in mind this problem is usually seen in vehicles with over 150,000 miles which have been poorly maintained. The solution to this problem is called De-Carbonizing. It usually costs around two labor hours at a smog check repair station. It will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx. ( Engine has close to 200,000)

5. Engine Overheating - Inadequate engine cooling can will high NOx. If your vehicle's cooling system is not working efficiently, (i.e. bad radiator, thermostat, hoses) high NOx will be created. Remember high NOx nitrous oxide is created when an engine's combustion chamber temperatures reach over 2500F. You will want to make sure your vehicle's cooling system is working properly, and your vehicle's temperature gauge is always indicating normal.

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