Dkakd wrote:
> My 1990 acura integra did not pass Virginia emissions due to high CO2 at 25
> MPH. I think limit was 80 PPM and it tested at 140 PPM. It has news plugs,
> clean filters, and 173,000 miles.
>

recent oil change? drive at highway speeds for about a half hour to get
the engine nice and hot? O2 sensor (s?) ever been changed?

according to what i posted before, it *looks* like your O2 sensor/s
is/are marginal.


was it CO? or CO2?

> Is this a simple mixture adjustment? Thanks,

id probably take it to a mechanic, see what they say, and then do that.
isnt there anything on the web that generally will tell what a
particular high reading is indicative of?

sure...

************************************************** ******************************

What causes high HC (hydrocarbon)? High HC is caused by incomplete
combustion; in other words, the air and fuel that went in to the
combustion chamber was not completely burned, now the unburned fuel has
ended up in the tailpipe. Problems that can cause incomplete combustion
include:

* An ignition misfire. If a spark plug does not spark, the air/fuel
mixture in the combustion chamber does not burn and then goes out the
tailpipe.
* Incorrect air fuel mixture. If there is not enough fuel in the
combustion chamber to ignite, the fuel that is there goes out the tailpipe.
* Low compression. If the compression is too low the air/fuel
mixture will not ignite and the unburned fuel will go out the tailpipe.
* A bad catalytic converter. The converter lives in the exhaust
pipe and burns unburned gas as it passes through.

What causes high CO (carbon monoxide)? High CO is caused by a rich
air/fuel mixture. The air fuel ratio should be 14.7 parts air to to 1
part fuel. Problems that can cause a rich mixture include:

* Problems with the feedback system (the system that regulates the
fuel being added to the engine based on the amount of oxygen in the
exhaust).
* Problems with a computer sensor such as the coolant temperature
sensor, air flow meter, MAP sensor, etc..
* Problems with the fuel pressure. Fuel pressure that is too high
can cause a rich mixture.

What causes high CO2 (carbon dioxide)? High CO2 is the product of a good
running engine. The better your engine runs, the more CO2 it produces.
The only way to reduce CO2 emissions is to buy a fuel efficient car. The
bigger your gas guzzler, the more CO2 it makes. This is what's so sad
about the recent SUV trend. In addition to depleting the worlds oil
reserves, and putting our country in a position where "we will go to war
to protect our oil supply", the trend of building increasingly
inefficient behemoths is making the planet a less hospitable place for
our species (and others) by contributing to global warming.

************************************************** *************************

What causes high O2 (oxygen)? High O2 can be caused by a lean air/fuel
mixture, but most of the time, noticeably high O2 is caused by either a
leak in the exhaust pipe allowing air to enter, or air injection pumping
air into the exhaust (this is done on some cars to aid in the burning of
HC). High O2 is not a problem unless the smog machine decides the
exhaust sample is too diluted to use; in which case, the car may fail
the smog test for dilution.

What causes high NOx (nitric oxide)? NOx is not measured in our area
currently, but if your car is registered in an enhanced area (an area
that requires testing of NOx), you may run into this problem. High NOx
is caused by high combustion temperatures and pressures. Problems that
can cause high NOx include:

* An inoperative EGR system. The EGR system was designed
specifically to reduce NOx; that's it's only function. The EGR, which
stands for Exhaust Gas Recirculation, allows exhaust gas to enter the
combustion chamber through the intake. The exhaust gas has a cooling
effect on the combustion chamber.
* Over advanced ignition timing. The more advanced the ignition
timing, the higher the combustion chamber temperatures.
* Overheating. If the engine temperature is too high the NOx
emissions will go up.
* Lean air/fuel mixture. If the air/fuel mixture is too lean the
combustion temperature will go up.
* Compression over specification. Normally when we think of engines
aging we think of the compression going down. However, there are a
couple of ways the compression can increase as the engine is used. One
is carbon buildup on the tops of the pistons. When carbon forms on the
tops of the pistons, the combustion chamber area decreases and the
compression ratio increases. The carbon can be manually scraped off the
tops of the piston to correct this problem, but that would require
disassembling the engine. Click here for cheap alternatives.
* Mysterious reasons. Sometimes NOx is too high and there's no
obvious cause: the EGR works, the timing and advance work normally, the
engine temperature is within range, the air fuel mixture is good, and
the compression is within spec.. When this happens you can try a little
tweaking. If there are two thermostats listed for the car, use the
cooler one. If there are two spark plugs listed for the car, use the
cooler one. Retard the timing 2 degrees (the maximum allowed). Clear out
the EGR passage even if the passage seems fine. Cross your fingers.


>
> Dan