[S-cars] Failed Emissions, too high HC count

[CyberPoet]

High hydrocarbons... Here goes:

High hydrocarbons result from incomplete fuel burn during detonation.
This is usually a result of too rich a mixture level (due to bad idle
mixture control, such as a failed/failing oxygen sensor), or too rich a
mixture level at one particular spot in the cylinder (such as from a
poorly misting injector).

1. Replace the oxygen sensor (old name: Lambda sensor, for those of us
who predate them) -- cost, about $30;

2. EASIEST: Drive your car until the gas tank is virtually empty. Add
12 gallons of premium fuel and a can of good quality injector cleaner.
Drive again until the fuel is virtually out, refill the gas all the way
with the highest octane unleaded gas you can buy -- and then promptly
change the oil & oil filter (injector cleaner breaks down oil's
viscosity retention). Cost, about $45 (includes 12 gals of fuel, 1 can
of injector cleaner, 1 oil & filter change).

2A. MOST EFFECTIVE FOR THE COST: If you have a few hours and access to
an ultrasonic cleaner, remove your injectors, insert them into the
ultrasonic cleaner (with liquid carb cleaner, not jewelry cleaner)
over-night, then reinstall. This infinitely more effective than 2, but
most people don't like the level of work and don't want to buy an
ultrasonic cleaner ($40 - $150, depending on source, size).

2B. CHEAPEST TO START & MOST DIRECT: Yank your injectors 1 by 1, having
disconnected the spark plug leads, place them over a large metal can
and have someone turn over the engine momentarily. Look at the spray
pattern -- does it look like a very fine mist, or more like a couple
tiny streams? If the answer isn't a fine mist, either use the method in
2A to clean it & retest, or go directly to replacing it.

3. Replace or clean all your spark plugs. On Audi's I generally
recommend replacing them because though not cheap, it's effective more
often than I care to mention. If you have a spark plug cleaner (about
$20 - $25 through JC Whitney -- sand blasts the existing plug), use it
IF AND ONLY IF your center electrode (A)  isn't thin as wire, and (B)
isn't platinum coated.

4. Make sure you've had the car running for an hour before you get to
the testing center. A hot engine traditionally produces substantially
fewer hydrocarbons, because more fuel burns in the exhaust headers/cat
when they are truly hot.

5. Adding 5% to 10% alcohol to your gasoline content will drive the
total HC availability down slightly and increase the burn level
(usually good for about a 10%  - 15% decrease in the final HC count).
This is in essence a cheat, and use it only as a last resort if you're
borderline.

Retest.

If you fail again, it's time to play find the bad injector(s) and
replace it/them...

Cheers!
=-= Marc Glasgow


On Tuesday, March 18, 2003, at 01:08 AM,
s-car-list-request at audifans.com wrote:

> As you can see, I failed the idle HC test. The S4
> could use an oil change. Might take a look at the
> plugs and at the next tech event, try and hunt around
> for any possible vacuum leaks. Perhaps a new O2 sensor
> is in order?
>
> Thanks for any help