retard the timming a degree or two do the test then put it back to spec, that may work.
another thing to try would be to add gas line antifreeze / methyl hydrate (same thing) but you have to add quite a bit to make this work exactly how much im not sure of,
another thing worth a shot is a seafoam treatment, to clean the intake, valves, and combustion chamber.
other than that try a basic tune up, oil, spark plugs, cap and rotor, fuel cleaning, a
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IDLE EMISSIONS
A vehicle that has sharply elevated HC or CO emissions at idle will usually have a noticeable misfire and/or rough idle. The most likely causes here would be:
Fouled spark plug(s);
Shorted spark plug wire(s) or defective plug boot(s);
Vacuum leak;
EGR valve stuck open;
Burned exhaust valve;
Misadjusted throttle body air/fuel mixture; or
Misadjusted carburetor idle mixture.
An extremely rich fuel condition can also cause elevated HC and CO at idle, while an extremely lean condition will only cause HC to rise abnormally. A leaky EGR valve can act like a vacuum leak and cause a lean misfire at idle.
HC and CO will be somewhat higher as a cold engine warms up because the fuel system may still be running in open loop. Until the engine reaches a predetermined temperature and/or the oxygen sensor gets hot enough to produce a good signal, the PCM will supply a relatively rich mixture while the system is in open loop. A faulty thermostat that is stuck open or a defective coolant sensor may prevent the system from going into closed loop.
NOX emissions are always lowest during idle and decel because that�s when engine load and combustion temperatures are lowest.
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Carbon Monoxide:
Measured in percent, this is the result of incomplete combustion. In other words, the fuel mixture has been compressed and ignited, but could not complete the combustion process due to the lack of oxygen. This failure is always mixture or ignition timing related. The ideal reading for CO is 0%. A normal reading for CO is usually around .25 to .75% with 1.2% being the failure mark in most areas for vehicles 1984 and newer. Earlier cars are allowed higher readings. Any car equipped with an Oxygen sensor will try to run under 1.0% as measured before the Catalytic converter (use that test connection for set-up). A vehicle with a CAT, O2 sensor, and an AIR system (Air Injection Reaction) will read almost 0% with everything working properly.
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Emission Fail
Linear Mode
