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Old November 20th 05, 05:12 AM posted to rec.autos.tech
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Default Failed SMOG, now what???


> The emission problem could be o2 sensor, catalytic converter or EGR
> valve. Or even more than 1 of the 3. So this could cost me a lot.



1. In what exact ways did you fail the smog test? Usually they give
you a printout with specific tests and their results.


2. What makes you suspect those particular parts? Smoggability
problems can come from a lot of sources, and shotgunning parts at them
is not nearly as efficient (or cheap) an approach as diagnosing what's
wrong.


3. Do you also have driveability or gas-mileage problems or just too
much of one or more of the specific kinds of pollution they check?

4. How long since the last general tune-up (plugs, cap, wires, rotor,
check ignition timing)?

As for the parts you mentioned: Generally speaking, the EGR valve
lends itself to simple go/no-go diagnosis and is not too terribly hard
to replace -- see the repair manual. The O2 sensor isn't hard to
replace on most cars, but mind the precautions so you don't slay it.
These are both usually somewhat comparable in techniques and difficulty
to removing and replacing spark plugs, just to take an example lots of
people are familiar with. The cat is in an awkward location, involves
some physical violence to remove and is by no means cheap... and
besides making sure it's realy the problem, you want to make sure the
upstream components are good so you don't just kill the new one.


Over to you...
--Joe

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