Beloved Leader wrote:
Dave Plowman (News) wrote:

Here are the results of my latest test:

Idle 538-540 rpm according to the test machine's display. (Should be 550)
HC, ppm: 15 mph: limit 55; actual 59 (fail)
HC, ppm, 25 mph: limit 100; actual 79 (pass)

CO, %, 15 mph: limit 0.22; actual 0.01 (pass)
CO, %, 25 mph: limit 0.32; actual 0.04 (pass)

NO, ppm, 15 mph; limit 720; actual 136 (pass)
NO, ppm, 25 mph; limit 700; actual 188 (pass)

Can you also post the CO2 and O2 readings? I won't know what they
mean, but someone will.

The only manual I have for the car is a Haynes manual, the one for
full-size GMs. There is a Haynes emissions manual, I think, but I don't
have it. I am within two miles of a Cadillac dealer and within four
miles of a community college with an automotive program. The community
college has a library of factory manuals and loads of CDs too. I'll be
able to pick a lot of brains if need be, but I want to do as much of my
own homework as I can first. Virginia's DEQ office is a local call.

I once glanced at the Haynes emissions manual and found it to be little
mroe than a rehash of the emissions chapters from other Haynes books.
It lacked the hundreds of pages of diagnostic tables found in the
Mitchell and factory manuals. That community college may not only let
you see the books but even fix your car at low cost, but don't be
surprised if they want to keep it for a few days.

Are you using only GM ignition parts -- AC plugs, wires, rotor, and
distributor cap? Some plugs don't substitute well, even when they're
supposed to, and trick wires (magnetic supression, as opposed to
resistive supression) can cause problems. I wouldn't even try AC
Rapidfires, simply because they're not factory original equipment.
Some brands of rotors and caps are made of bad plastic that cracks from
high voltage. I realize you changed all the vacuum hoses, but did you
check for vacuum leaks at the intake manifold gaskets and base of the
carburetor by spraying there with choke cleaner?

I did turn down the idle from its initial ~800 rpm to the specified
550. At this rpm, the engine sometimes stalls. I'll probably have to
turn it back up after I've passed the test.

Try injecting propane or choke cleaner into the air intake (leave air
filter and cover in place -- prevents fires in case of spit back) for a
few seconds. If the idle (set to about 550 RPM) smooths out (injecting
chemicals will make it speed up by as much as 200 RPM), suspect a
vacuum leak or a carburetor problem. The idle mixture solenoid has
been troublesome in some feedback carbs. I don't know if there's any
kind of idle speed regulation (throttle air bypass valve, throttle
kicker or motor), but a carburetor problem may be completely unrelated
to your high HC.

By the way, run the air conditioner compressor for at least 10 minutes
in a row each week, even during the winter, to keep the shaft seal from
drying out. You have a Freon R-12 system and don't want any of that
gas to leak out, and you don't want to convert to R-134a the wrong way
(cheap, quick conversions don't perform well and have high failure
rates).

I don't see the purpose of top engine cleaner here, and I'm surprised a
dealer mechanic would recommend it, at least not without first reading
out the CCC data stream during engine operation to find any
abnormalities (temperatures, barometric and manifold pressures, oxygen
sensor voltage, throttle position, fuel mixture solenoid duty cycle,
etc.).