High CO tends to come from an overly rich air-fuel mixture and/or unburned
fuel.
I don't know the state of tune of your car or the last time the carb was
rebuilt, but if it's dumping in too much fuel or not using it up, you
should
be able to get the car to pass by addressing one or both of those. Start
with the easy stuff: fresh spark plugs (Autolite #85), properly set
timing,
a fresh oil change, tank of gas and air filter. After that, consider a
carb
rebuild, new plug wires and/or even a new ignition coil, as a weak spark
will result in poor combustion.
One thing I always make sure of before a smog check is to drive the car
for
a good half-hour on the freeway, with a few good sprints for good luck.
Often an under-warmed-up engine will register high hydrocarbon levels
rather
than high CO, but high HC is also a result of unburned fuel (or in the
case
of newer cars, a catalytic converter not yet fully warmed up, not an issue
with your '69).
What state do you live in, and what kind of emissions testing do they do?
(In CA, the car goes onto a dyno and they test at 15 mph and 25 mph, so
it's
a pretty grueling, or at least revealing, test.) 3.75% CO is a very high
standard (meaning not stringent). Also, what's the odometer mileage on
your
car?
Here are the results of the last time I had my '78 NYB smogged. Granted,
it's a 17,000-mile car with a Electronic Lean Burn and a catalyst, but
note
the maximum allowable levels and how far my car comes from it, since this
engine was not originally available in CA because it failed to meet
emission
standards. I offer this only as encouragement that a proper state of tune
can help a lot, even on a car that's obviously only driven very
occasionally.
------
All numbers are listed as MAX / AVG / MEAS, where:
- MAX = the legal maximum allowed before the car fails
- AVG = the average figures for all passing vehicles
- MEAS = my car's readings
15 mph MAX / AVG / MEAS
------ -------------------
HC (ppm): 175 / 47 / 33
CO (%): 1.17 / 0.20 / 0.13
NO (ppm): 1215 / 554 / 492
-----------------------------
25 mph
------ -------------------
HC (ppm): 142 / 37 / 43
CO (%): 0.97 / 0.17 / 0.12
NO (ppm): 1075 / 468 / 468
-----------------------------
Hope this was helpful. Let us know what you do and how much it helps!
Chris in LA
67 Crown (125,000 miles, and always passed when it had to be tested)
78 NYB Salon (just a 17,000-mile baby)
On 6/27/06 10:53 PM, john sadowski at jsadowski@xxxxxxx wrote:
Well, Its that time again. I had to go through emmissions 4 times last
year
before finally passing. I went today & it failed the carbon monoxide test
under load. The standard is 3.75 & it went through at 4.98. The other 3
tests passed by a very comfortable margin. They were supposed to be
exempting collector cars here, but the law has yet to take affect & they
don't know if it will. I've been driving the 69 occassionally now & it
runs
pretty well. I was surprised that it didn't pass.
John
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