You are
currently in section:
Ask The Mechanic
Systems:
Engine
Fuel
Exhaust
Cooling
Drivetrain
Suspension
Electrical
Body
Brakes
Heat/AC
Oil
/ Lubrication
Garage Tips:
Find
a good mechanic
Communication
is key
Scams
to avoid
Ask
the mechanic
Do it yourself:
Easy
stuff
Intermediate
Advanced
Tools
for the DIYer
Latest
Blog Posts
|
Ask
the Mechanic
brought to you by:
Austin C. Davis
Author of:
"What
Your Mechanic Doesn't Want You to Know"
Reader Question: "Hello
Austin, I recently had the "service engine soon" light come
on my '94 Buick Century. Took it to my mechanic, and he said it was the
EGR valve which he changed out for over $500. The light came on again
within 24 hours and I took it back. He said he tightened the fittings,
and said that the EGR computer may need to be replaced!??? Since then
the "service engine light" has gone off and come back on several
times. What is going on?"
I think you should ask for your money back. The onboard
computer system in your 1994 Buick Century is fairly rudimentary compared
to newer models and does not give the most in depth diagnostic information.
The EGR valve is fairly expensive for your Buick, and the price sounds
ok. However, if the problem is still not resolved you should ask to have
your old valve re-installed (you did ask to keep your old parts and their
original boxes didn’t you---?)
Tightening the fittings is a cop out, and is probably his way of saying
“I don’t know how to fix it”. The SES (Service Engine Soon) light can
be very tricky to turn off sometimes…..it is best to diagnose the problem
when the light is on. Every time you turn off the car and re-start the
engine, the onboard computer does a sequential self check of all the sensors
and components on the car. If the car has not been driven far or long
enough, the system will not be able to complete its test. This explains
why the Check Engine Light won't always come on. So as you drive, the
light might come on and stay on as the computer finds a fault during its
routine check list. Also the faulty component might only malfunction at
a certain speed or temperature which is VERY common.
My guess is that the EGR valve is NOT the problem, but your mechanic received
an EGR trouble code from your computer system while running a diagnostic
test. There are more components of the EGR (Exhaust gas Re-circulation)
than the valve and any of those can cause an EGR trouble code. If you
can’t get your money back, have him try his second diagnosis - a new computer
(There is no such thing as an "EGR computer" on this car)at
HIS expense to see if the problem goes away. If you are a fairly regular
customer at this shop, he will want to fix this problem for you and keep
you happy. The price of an after-market computer should cost him about
$100, and the installation is simple and quick. He will not be out as
much money as you invested in his mis-diagnosis.
My gut says that this mechanic is not very computer savvy and this is
probably over his head. The computer is usually the last thing to be replaced.
Think of your home computer…it is usually a software problem that causes
a glitch and not a problem with the hard drive or mother board.
This is what would have happened at my shop. This is how your mechanic
should approach tracing and repairing an intermittent electrical problem.
- Read onboard car computer system trouble codes
- Re-set car computer memory and test drive the car
at freeway speeds as the repair manual describes to see if the code
re-appears
- If no code appears, give car back to customer to
drive and monitor
- If a code does appear, retest all components involved
with that code. If an EGR is determined to be faulty, replace with new,
and KEEP old part IN ORIGINAL box for 30 days with customer name on
it---or give old part to customer to hold.
- If light returns, re-test and see if same trouble
code returns. If same code appears (scratch head) and try something
else, such as inspection of EGR vacuum lines, until check engine light
is out.
- Once light is out, re-install OLD EGR valve and
give credit to customer. Bill customer for ALL time involved and only
for parts that were used.
- Return all non-used parts to vendor.
We have rows of old parts on our shelves that we use as test parts in
cases like this. Feel free to ask your mechanic to try a good used part
first, if he is not 100% sure that the part will fix the problem. The
mechanic might feel better about the situation he is in if he knew you
understood he is not totally certain about his diagnosis.
Be patient. Sometimes these silly check engine lights can be hard to track
down even with the best diagnostic equipment and trained mechanic.
Incidentally the dash warning lights are color coded
A Yellow Warning light,
like the Check Engine Light, means nothing terrible has happened, but
have the car checked out at your convenience.
A Red Warning light
means pull over now, and turn off the engine.
I
talk about other problems like this in my eBook
"What Your Mechanic Doesn't Want You to Know"
Which just happens to be on sale
right now
Along with two free money saving reports with your order
Click
here now
I hope this helps. 
|
