The VX just failied emmissions also. Not ONx but HC. I googled it and found these common causes of failure..
EXCESSIVE HYDROCARBONS (HC)
These emissions result from unburned fuel. Check the following areas for problems: - Internal engine trouble - Faulty air pump - Ignition system - Exhaust gas recirculation system (EGR) - Catalytic converter - Gas Cap
EXCESSIVE CARBON MONOXIDE (CO)
High amounts of carbon monoxide occur in a rich fuel mixture, meaning there's either too much or too little air reaching the combustion chamber. Check for problems with the following: - Mis-adjusted carburetor - Faulty fuel-injection system - Dirty air filter - Worn rings or valve guides - Air pump system
OXIDES OF NITROGEN (NOx)
High levels of NOx can be caused by excessive temperature in the combustion chamber of a damaged catalytic converter. Check for problems with the following: - Air injection system
Don't get your hopes up for that one. We've been using an easy button at the office for weeks and it's a big disappointment. (Seriously...one of our admins got one and put it on her desk.)
Dan's problem is encouraging because excessive hydrocarbons = should be using less fuel than it is, hence the potential for huge numbers once he has it in tune. Of course, I'm assuming that it won't be a huge $$ fix...
Matt: I don't know what you've done, already, but from my perspective, I'd try to find out what is causing it to overheat. If your having to run your heater as an auxiliary radiator, something's either causing it to lean out, tremendously, or your thermostat isn't opening, or something. I've had a lot of problems with my 87 Civic, in regard to overheating, but I am pretty sure that most of my problems stem from a loss of fluid, when the system get's under pressure. Every time I check, it is only down maybe 2 cups of water, in the radiator, but that 2 cups is enough to make the thermostat not get water, and hence it doesn't open, which in turn causes it to get hotter, which in turn causes more pressure, causing more water loss. In every instance, when I have checked it, it has been down by a couple of cup's of water.
In my case, I found I had a radiator which was getting pretty tired, which I have replaced, but which hasn't really been tested because it's sitting, waiting for me to finish figuring out a totally unrelated issue.
In any case, on the 87, the radiator seems to sit lower than in the 89, and it seems to be extremely critical for all of the air to be evacuated, all of the time.