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Failed CA Smog Check II



 
 
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Old February 8th 05, 01:12 AM
TheSmogTech
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Default Failed CA Smog Check II

Information Retreived From http://www.smogtips.com

SMOGSMART VIR REPORT - 1997 FORD EXPLORER 4.0 LITER ENGINE
SmogSmart VIR Report #153337

Your vehicle failed for: High CO, NOx and HC at 15 and 25mph. There may
be a possible rich mixture. There are potential ignition concerns.
Vehicle failed CO with very high numbers. This condition is usually due
to a "rich fuel mixture". CO levels of this amount in most cases
automatically produce high HC. The condition which causes the high HC
(due to high CO) is called a "Rich Misfire". The diagnosis for this
failure should include close inspection of your vehicle's fuel
management and control systems. The engine ignition system must also be
diagnosed. HC faults (if not related to fuel mixture problems) are most
often due to improper fuel ignition.

Some Specifics: First off your vehicle's failure will require some
diagnostic time, due to the fact that we normally see vehicles with
failures in more then one of the three emissions categories. When a
vehicle fails all three categories (HC,CO and NOx), or at least
produces high results in these categories, there is usually more then
one emissions component at fault. And/or, not all of your vehicle's
engine's cylinders are burning fuel at the same efficiency.

How a Rich Misfire causes high CO: CO stands for Carbon Monoxide. It is
a by-product of incomplete combustion, more then often related to the
presentation of too much fuel to the combustion chambers. The spark
created at the sparkplug can only burn a small amount of fuel, the fuel
it cannot burn is sent out the tailpipe and will normally contain high
levels of partially burned fuel(CO) and raw fuel(HC). In a "Rich Fuel"
condition diagnosis would begin with inspecting all possible mechanical
faults which could cause excessive fuel to enter the combustion
chambers. This diagnosis would include inspecting your vehicle for high
fuel pressure, intake vacuum leaks, air restrictions and/or leaking
fuel injectors. NOTE: A dirty air filter may restrict ample air from
entering the combustion chambers. The lack of air will create a rich
fuel condition and result in high CO. If your vehicle has not had a
tune-up in the last 15,000 miles, we recommend a quick service from a
local smog stations. A basic tune-up should run between $120.00 to
$220.00.

As part of the mechanical system diagnosis, the vehicle's EVAP system
would be inspected also. The EVAP system is designed to introduce gas
tank and/or carburetor fuel bowl fumes into the combustion chambers.
These gases(vapors) are just as combustible as the actual fuel in your
gas tank. If they are not routed into the combustion chamber, the
vapors build up within your engine's fuel system and eventual escape
through a vent into the atmosphere. So in-order to eliminate this
problem auto manufactures have designed the EVAP system to make use of
this vapor. If your EVAP system is not functioning properly it can
present these vapors to the combustion chamber at the wrong time and/or
to often, causing a rich fuel mixture and increased CO in the exhaust.

Once the mechanical faults have been factored out, the focus would turn
to the vehicle's electronic fuel control system.

Fuel distribution to your engine's combustion chambers is controlled by
your vehicle's ECU(Engine Control Unit) and fuel injectors. In order
for your engine to pass a smog inspection, fuel delivery must be
preciously controlled to produce the least emissions. If the injectors
do not present enough fuel to the combustion chambers, this would cause
low CO emissions. In a situation where the injectors present too much
fuel, this would causes high CO emissions. In order for the ECU to
estimate the right amount of fuel to distribute, it needs to know how
much fuel is currently in the system. This way it can always maintain a
proper Air/Fuel ratio and keep emission levels at their lowest. The
main component responsible for letting the computer know how much fuel
is in the exhaust system at this moment, is the Oxygen Sensor. The
Oxygen Sensor sends an electrical signal to the ECU, letting the
computer determine exactly how much fuel it should continue to deliver
to the combustion chambers. If for any reason the 02 sensor (oxygen
sensor) does not send accurate information to the computer or it is
"lazy" in sending the correct signals, the fuel delivery program can be
altered. The computer may then present either too much or not enough
fuel to the combustion chambers and therefore cause an emission
failure.

We recommend looking into the rest of the fuel management components
also. In a computer controlled engine such as this, there are several
components which also play a role in determining Air/Fuel ratio. Along
with the Oxygen Sensor, components such as the, TPS (Throttle Position
Sensor), ECT (Engine Coolant Temperature Sensor) and the MAP (Manifold
Absolute Pressure Sensor) sensors also send vital engine information to
the computer which is used to determine proper air to fuel ratio. If
any one of these components are defective they can alter the fuel
delivery program. A smog service station can diagnose each component
and report it's condition.

What does HC have to do with the High CO: There is a condition called
the "Rich Misfire". This condition is created, when for any reason, the
combustion chambers receive too much fuel, causing the fuel that is
delivered to burn improperly and leave behind high levels of raw
fuel(HC) and partially burned fuel(CO). As mentioned, fuel distribution
to your engine's combustion chambers is controlled by your vehicle's
ECU(Engine Control Unit) and fuel injectors. Vehicle's producing high
HC for fuel management reasons usually begin producing normally HC
levels once the fuel problems are corrected.

However for those vehicles suffering from high HC not related to fuel
management, should have the engine ignition system closely inspected.
High HC can be caused by improper spark delivery. During the combustion
process any number of engine conditions can cause emissions failures.
However because of the fact that out of the three systems your engine
relies on to produce combustion (Air intake, Fuel Distribution, Spark
Control), the Spark system has the highest likelihood of becoming
defective sooner then the rest of your engine's due to the fact that
sparkplugs and spark wires are constantly exposed to high temperatures
and high voltages. You must insure your engines ignition system is
functioning properly, by inspecting all the sparkplugs and their wires.
If any of the plugs look worn out or have excessive carbon build-up
replace them immediately. You may use any brand of product designed to
work in your vehicle. Most of the time aftermarket parts (non-factory)
will be much cheaper. More then likely you will see an instant
performance increase once these corrections are made.

Why is my vehicle's NOx so high: The reason vehicles generally
encounter NOx failures is usually due to one of two faults. The first
may be a malfunctioning EGR valve and/or plugged up EGR ports and
passages. EGR stands for exhaust gas recirculation. And that is exactly
what this component does. The EGR system recirculates burned up exhaust
gases back into the combustion chambers. Since these recycled exhaust
gases have already been in the combustion chambers once, they have
burned up most of their fuels, means there is now much less real fuel
in the chambers to ignite. This keeps the chamber temperatures down and
thus reduces NOx emissions. The EGR valve should be inspected to insure
its proper operation. A working valve should be able to open its
passage using manifold vacuum. Manifold vacuum is created during the
engine's intake cycle. The high demand for air during this cycle
creates a vacuum within the engine's intake manifold. This vacuum is
then used to control several important functions within the vehicle,
including controlling the EGR valve. Some vehicles even rely on this
vacuum to control their heating and air-conditioning components. The
EGR system is prone to collecting carbon build-up. Some vehicle
manufacturers recommend cleaning this component an a regular basis.

High NOx may also be caused by vacuum leaks to one or more cylinders.
Vacuum leaks are open passages, normally due to defective gaskets
between two engine components. These leaks will allow the suction of
additional and un-metered air (oxygen) into the combustion mixture or
exhaust (depending on where the vacuum leak is located) disturbing
pre/post fuel combustion and increasing NOx emissions. Vacuum leaks can
be difficult to locate if they are present at locations not easily seen
by the naked eye. Smog repair stations have special tools and methods
designed to locate vacuum leaks quickly.

Final Comment: There will be a few steps involved in finding out the
root cause for your vehicle's failure/s. You should consider now this
will take some time and money. The emissions system/s responsible for
causing high NOx, CO & HC will have to be individually diagnosed, and
step-by-step eliminated as faults. Please Remember: California law only
allows State Certified Smog Repair stations to conduct smog inspections
and smog repairs on vehicles being driven in California. We highly
recommend you search our database of SmogTips State Certified Smog
Repairs stations. SmogTips Certified Stations are pre-screened for
quality repairs, fast friendly service, and reasonable prices.

SMOGTIPS SMOGSMART VIR REPORTS - Save Money. Smog Smart. SmogTips.com -
"California's Leading Smog Check Support Group" - 1-877-SMOG-TIPS
www.smogtips.com



DJD wrote:
> Anyone?
>
> DJD wrote:
> > This is the 1st year I've had to get the new dynamic Smog Check II

and
> > my Sport failed miserably. Hydrocarbons almost 300, CO at 10, even

after
> > a tune-up and injector cleaning. After running a diagnostic I also
> > replaced the thermostat (again). I had replaced it and the sending

unit
> > some time ago, but there was no change, so I assumed the gauge was
> > busted. However, it clearly is working properly now, which was

confirmed
> > with an IR thermometer in the water lines. So apparently I had

replaced
> > one bad thermostat with another. My mechanic believes that the open


> > thermostat and resulting cool engine temp caused the fuel mixture

to be
> > richer than it should have been, fouling the O2 sensor and

catalytic
> > converter and that both will need to be replaced. He will run his

own
> > diagnostic, but of course, a bad CC won't show up on it. However,

my
> > exhaust does have a slight rotten egg smell which he claims is
> > characteristic of a failed CC.
> >
> > The theory does make sense to me, but my knowledge of emissions

systems
> > is pretty limited. Does this make sense to those of you who are

more
> > knowledgeable about this? Also, what would reasonable replacement

and
> > labor costs be, keeping in mind that this is the SF Bay Area? I

know I
> > can't do the CC replacement myself, it requires cutting and

welding, but
> > how about the O2 sensor replacement? I also need to consider that

smog
> > check re-tests and manual checks are at no charge, so long as he

does
> > the work. A Smog Check II test runs $70, a manual check runs $45

and
> > he's already done 1 manual, plus the original test.
> >
> > Comments and suggestions welcome.
> >
> > FWIW, other than the emissions problems and a noisy PS pump, it

runs and
> > looks fine.
> >


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