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Subject:
Re: lamp replacement in dash on C5 help needed
Lines: 15
From: larrysb(at)aol.commode (nuke)
Date: 01 Nov 2003 11:42:02 GMT
Subject: Re: lamp replacement in dash on C5 help needed
________________________________________________
<< first it was the lamp that shows the temp, now it`s the lamp that
shows numbers 3 and 6 on the stereo....is this simply a job of
removing and replacing the bulbs or is there more to it....the dealer
said it could run as much as $1200.oo which I really don`t believe.
Any ideas ? >><BR><BR>
Usually they just change the radio.
Used GM radios are quite cheap and readily available on the used parts market.
Many people upgrade them.
--
Dr. Nuketopia
Sorry, no e-Mail.
Spam forgeries have resulted in thousands of faked bounces to my address.
From: norm peterson <hytussnospam(at)aol.com>
Subject: Re: lamp replacement in dash on C5 help needed
Lines: 2
Date: Mon, 03 Nov 2003 13:33:12 -0600
________________________________________________
thanks for the reply, I knew it had to be a rip......I`ll just upgrade
my stereo and do it myself
From: alicecooperrules12(at)yahoo.com
Subject: lance back for more humiliation
Lines: 313
Date: Tue, 05 Jul 2005 23:05:56 GMT
NNTP-Posting-Host: 209.115.153.53
________________________________________________
On Tue, 05 Jul 2005 22:41:08 GMT, Lance A Boyle <Lance_Boyle(at)shaw.ca>
wrote:
>half_wit_crossposting_cock_smoker(at)yahoo.com wrote:
>
>
>> all auto manufatures us EGR
>
>Nice cut/paste.
>
>Explain it to in YOUR own words hurc. Also, how does it relate to
>Diesel engines in particular.
>
lmfao
i offerd ya a teck manuall
cant you read
all you offer is your babble
yet ya claim the tech manuals are wrong
tell me lance
what you know that the guys that make engines dont ??
introducing an inert gas is hardly a throttle it does not control
engine speed
IT DECREASES HEAT foctard
lance please name one engine maker that doesnt use EGR
lmfao
>I`m also still waiting for the reference were I said Diesel engines had
>carburetors.
>
On Fri, 27 May 2005 02:16:39 GMT, Lance A Boyle <Lance_Bo...(at)shaw.ca>
>>>>You fucking moron. The throttle on a diesel engine is the butterfly
>>>>that restricts the intake airflow.
LMFAO
BWHAHAHAHAHAHA
still waitinf fo ya to show me a butterfly valve on a powerstroke
>Lance
>> lmfao
>> psssssst lance its called
>> EGR
>>
>> foctard
>
>You really have no clue about anything other than what you learned in
>your useless ast course. Do you ever read or study other material that
>isn`t on an exam? Your lack of knowledge about anything mechanical is
>astounding. Just because Ford uses EGR to control cylinder temp,
>doesn`t mean that the rest of the world does it that way. Do some
>research hurc, and stop looking like such a loser all the time.
>
>>
>> LMFAO
>> schools out
>
>HAHA. Does that mean you could actually teach me something about
>anything? Shit
lmfao
lance the more ya babble
the more retarded ya look
lance you just put your foot in your mouth
your the one that needs research
all auto manufatures us EGR
Understanding exhaust gas recirculation systems
By Henry Guzman
Exhaust gas recirculation (EGR) systems were introduced in the early
`70s to reduce an exhaust emission that was not being cleaned by the
other smog controls. Oxides of nitrogen (NOx) are formed when
temperatures in the combustion chamber get too hot. At 2500 degrees
Fahrenheit or hotter, the nitrogen and oxygen in the combustion
chamber can chemically combine to form nitrous oxides, which, when
combined with hydrocarbons (HCs) and the presence of sunlight,
produces an ugly haze in our skies known commonly as smog.
How to reduce NOx NOx formation can be reduced by:
Enriching the air fuel (A/F) mixture to reduce combustion
temperatures. However, this increases HC and carbon monoxide (CO)
emissions.
Lowering the compression ratio and retarding ignition timing; but this
leads to reduced performance and fuel economy.
Recirculating some exhaust gases.
How EGR systems work The EGR valve recirculates exhaust into the
intake stream. Exhaust gases have already combusted, so they do not
burn again when they are recirculated. These gases displace some of
the normal intake charge. This chemically slows and cools the
combustion process by several hundred degrees, thus reducing NOx
formation.
The design challenge The EGR system of today must precisely control
the flow of recirculated exhaust. Too much flow will retard engine
performance and cause a hesitation on acceleration. Too little flow
will increase NOx and cause engine ping. A well-designed system will
actually increase engine performance and economy. Why? As the
combustion chamber temperature is reduced, engine detonation potential
is also reduced. This factor enabled the software engineers to write a
more aggressive timing advance curve into the spark timing program. If
the EGR valve is not flowing, onboard diagnostics (OBD) systems will
set a code and the power control module (PCM) will use a backup timing
curve that has less advance to prevent engine ping. Less timing
advance means less performance and economy. Do your customer a favor
and fix those EGR codes that you may have previously deemed as
unimportant.
Evolution of the EGR systems The first EGR valves appeared in 1973 on
GM cars. Bolted to the intake manifold next to the carburetor, it has
ports to the intake and exhaust manifolds. It has a diaphragm that
pulls open a valve stem, which allows exhaust to enter the intake
manifold when ported vacuum is applied to it. Ported vacuum increases
with throttle opening. A thermal vacuum switch prevents vacuum from
reaching the EGR during cold engine starts. This system had many
problems. It would often open too soon or too much, which caused a
hesitation on acceleration as massive amounts of recirculated exhaust
hit the combustion chamber. Many people simply disconnected it when it
began to cause problems because they did not understand its importance
or design. By 1975, if you unplugged an EGR valve, you`d have a
driveability complaint of engine ping. Manufacturers and technicians
of that era experimented with vacuum orifice restrictors and vacuum
delay valves to try to find a happy medium between clean air and
performance.
Closed loop systems By 1981, closed loop computer controls were in
place. EGR flow was now more carefully controlled with dual diaphragm
and back-pressure EGR valves. Modulating the vacuum to the EGR valve`s
pull, open diaphragm controlled the flow of recirculated ex- haust.
Called by various names such as amplifiers, transducers and
modulators, both remote and integral vacuum modulated devices were
used. The flow of vacuum was further controlled by solenoids that
blocked the vacuum ports until certain criteria were met such as
engine temperature, rpm and manifold absolute pressure (MAP).
As the manufacturers began to use these complex schemes with vacuum
amplifiers, delay valves and solenoids, they added a lot of
"spaghetti" to the engine compartment. Plastic vacuum connections
would break and rot with age and were not very reliable. Vacuum
diagrams were invented and became essential to the smog driveability
technicians of the day. As these systems evolved, they had fewer parts
and less vacuum tubing. This was achieved by the use of pulse width
modulated EGR solenoids. The PCM controlled EGR flow through the use
of these solenoids to modulate vacuum to the EGR valve instead of just
turning it on or off periodically.
What is pulse width modulation? Let`s take a moment to discuss how
computers think so we can better understand this common form of PCM
control. Computers are binary. The machine language they operate in
consists of only two variables: on or off, true or false, high or low.
That`s the only way a PCM can think. As a result, computer controlled
outputs are always on or off, high (system voltage) or low (ground).
Therefore, a computer output is always a square wave, or an on-off
step when viewed on a lab scope. The high portion of the waveform will
usually be battery voltage or PCM voltage of approximately 5 volts,
with a few exceptions where the PCM operates at a different voltage.
Once the PCM receives its inputs, such as rpm, throttle angle, coolant
temperature and MAP, it then calculates a response based on the
software program that is embedded into it. Next, it makes its decision
and sends a command in the form of a pulse width modulated signal to
turn the EGR solenoid on and off rapidly. The EGR solenoid has two
vacuum nipples. One side gets either manifold or ported engine vacuum.
The other nipple goes to the EGR valve. Its default position is to
block vacuum to the EGR valve. A vent is incorporated to bleed off
vacuum when the solenoid is being pulsed. Vacuum flows to the EGR in
rapid on-off pulses as the solenoid is commanded by the PCM.
OBD I systems With each succeeding year, the EGR designs became more
refined. The California Air Resources Board (CARB) liked GM and
Chrysler`s onboard diagnostic systems. In 1988, CARB required that all
cars sold in California be equipped with an onboard diagnostic system
and a "check engine" light to notify the driver of emission system
failure. By this time, all manufacturers had to have an EGR system
that was capable of alerting the driver if it was not working. OBD I
diagnostics and trouble codes were added in to flag opens, shorts and
sticking solenoids.
OBD II EGR systems OBD II requires that the EGR system be monitored
for abnormally low or high flow rate malfunctions. The EGR is
considered malfunctioning when an EGR component fails or a fault in
the flow rate results in the vehicle exceeding the Federal Test
Procedure (FTP) by 1.5 times. FTP is the government-mandated drive
cycle smog test that all new cars must pass and adhere to.
The diagnostic executive, also called the diagnostic task manager by
Chrysler, controls the EGR monitor. The executive is an OBD II
software agent given the task of managing all the onboard monitors and
the scan tool interface. The executive coordinates the sequencing and
actuation of all the monitor`s test routines. There are eight main
monitors whose sole function is to directly monitor and test the
components assigned to them to ensure they meet FTP standards for
life. These monitors are:
Catalyst monitor
EGR monitor
EVAP monitor
Fuel system monitor
Misfire monitor
Oxygen monitor
Oxygen heater monitor
Secondary air injection monitor
A closer look at the EGR monitor Monitor tests are both intrusive and
non-intrusive. An example of an intrusive test is when the EGR monitor
cycles the EGR valve during a condition when it normally would be
closed. In some cases, the customer may feel an intrusive test as a
slight miss.
The method of testing used by the EGR monitor varies according to the
manufacturer, but there are three main types.
One method includes looking for a change in manifold pressure as the
EGR valve is actuated on and off.
A second method involves cycling the EGR valve and looking for a
change in short-term fuel trim. When the EGR valve is opened, it
displaces some of the air fuel mixture. When the EGR valve is closed,
more oxygen enters the combustion chamber, which then leans the
mixture somewhat. The O2 sensor will respond with a lean signal to the
PCM, which in turn increases pulse width. This is called short-term
fuel trim compensation. The EGR monitor looks to see that all these
things are occurring as they should. It repeats the tests and averages
the results. Before the EGR monitor can begin its testing, it must
first receive clearance from the diagnostic executive. The executive
ensures that there are no conflicting conditions that would invalidate
the EGR monitor`s tests. For example, if the car had a lazy O2 sensor,
fuel trim compensation to the EGR opening and closing would be
inaccurate. Therefore, there are many safeguards built into OBD II to
prevent this type of occurrence from happening. OBD II also has
rationality checks. In other words, it uses deductive logic and
constantly compares its inputs against each other to make sure all are
in sync with one another. After the EGR monitor gets the OK to run its
tests, it uses strict enabling criteria to ensure accurate testing
such as:
Engine temperature more than 170 F.
Ambient air temperature more than 20 F.
Engine run time more than three minutes since 170 F.
Engine speed 2248-2688 (auto. trans.), 1952-2400 (manual trans.).
Manifold absolute pressure from 5-20 hg.
Short Term Adaptive Fuel Trim is adjusting pulse width by less than +7
percent and more than -8 percent.
TP sensor from 0.6 to 1.8 volts.
Vehicle speed sensor more than 40 mph.
The above is used for illustrative purposes only. Refer to your manual
or CD-ROM information system for specifics to the car you are working
on.
The third type of EGR monitoring design includes monitoring an EGR
position sensor and a back-pressure sensor. Some Fords use a
differential pressure feedback sensor that reads exhaust back-pressure
upstream and downstream of the EGR valve to determine its flow rate
and operation.
While OBD I systems would usually flag an inoperative EGR system, OBD
II systems are given the task of determining the correct amount of EGR
flow to keep the car running clean.
Next month, we will get into diagnosis, testing and repair techniques
for all the different types of EGR systems. I will also cover pattern
failures of all types, including mechanical problems such as plugged
EGR passages that can cause rpm specific misfire concerns.
Henry Guzman is an ASE master tech with L1 certification. He has 20
years of experience working as a technician on foreign and domestic
cars.
--------------------------------------------------------------------------------
ASA Main Page || AutoInc. Main Page
Implementing the new clean air regulations || NACE Coverage || A look
back at CARS `97 || Understanding exhaust gas recirculation systems ||
Is the chemistry right for sectioning repairs || How to work with the
media || Show owners critical to success of training programs ||
Hunting for profit || The training enigma - Part II || Guest
Editorial: Dream or Nightmare - Do the Homework || Tech Tips || News
Briefs || Taking The Hill || Around ASA || Shop Profile || Net Worth
|| Chairman`s Message
--------------------------------------------------------------------------------
AutoInc. Magazine ®, Vol. XLV No. 11, November 1997
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