'90 L98 Vert. Service Engine Light would come on after about 15 minutes of
driving. Any time I would turn off the engine, it would reset. Comes right
back on when it warms up. Took it to local Firestone. They said my EGR
valve was badly stuck. Said if I continue to drive as is, the Cats would
eventually load up with Carbon. They want $450!!! I think this is a bit
excessive. Is there something about an L98 that makes this a difficult job?
From doing some searches, looks like the going rate for the valve is around
Thanks for your input.
Dunno about space issues on a '90, but I did the one on our '95 in about
a half hour and that included waiting for the flat black paint to dry,
because the replacement was cadmium plated and the original was flat
black. I believe I gave about $65 for the valve at NAPA, so $70 is about
right. Firestone will charge you dealer retail for the valve, so
figure they will get what, maybe $140 for the valve, plus all the
"nickle and dime" stuff like handy wipes and environmental disposal, and
what ever other charges they can pad the bottom line with. Just make
sure you get a clean gasket surface before you bolt it up.
valve at $60/$65 and they have 2 numbers 2145535 and 2141429 (plastic
vacuum fitting). Airtex is $70 and a metal fitting but shows no gasket
with it so check before you get back to work and there is none,
FEL-PRO gasket part # 70954, and ACDELCO part # 10077547. Wouldn't be
a bad idea to remove the valve to take it with you, but before you do
that clean it and the manifold up and see if the diaphragm will hold a
vacuum and work the plunger, if so put it back with the new gasket.
The $450 repair just became a $2 job.
Take a close look. My '89, and I think all
of '85 - '91 had the EGR under the plenum --
not out in the open as in the LT1.
If this is the case, you'll need a set of
Torx bits and a flare wrench to remove the
plenun and the vacuum lines. It's tight but
you can get the EGR out without pulling the
As Bob says, get the little gasket for the
EGR. Shop around and get a partial intake
gasket kit...one with just the gaskets
between the runners and the plenum. New
throttle body gasket is also a good idea.
If the '90 has a MAF, remove it but leave the
throttle body hanging. Disconnect the vacuum
hoses to the plenum and check for an
electrical lead to a MAT sensor on the bottom
of the plenum ...might not be one on the '90.
Gently tap the plenum to break it loose
from the runners and lift it out, vertically
so as to not scratch the mating surfaces or
drop broken gasket material down the runners.
Should be about two hours coming apart, 30
minutes to swap the EGR and clean up the
intake mating surfaces and a couple of hours
putting stuff together again. If the car has
over 80K miles it might be good to clean the
inside of the plenum
Looks like you're making about $ 85 an hour
and have some "free" tools for the next job.
Six-pack isn't included in this pricing. (8-O
Suggestion: Not that I don't trust the
highly qualified Corvette specialists at
Firestone... however, before you leap into
this, dump the codes and make sure you're
dealing with an EGR issue.
The Haynes C4 manual has some tests that can
be run on the EGR. Making sure there's
vacuum to the EGR is a good idea-- a vacuum
leak would prevent the valve from working.
'89 auto / '02 6-spd
My answer is a little bit off topic but it concerns the egr valve. Don't
know where you live but if you don't have yearly smog tests to pass. I
suggest you block off the egr valve.
Now I don't have a 90s Vette but bear with me. On my 92 Ford Ranger, the
computer controls the EGR valve position using vacuum, then there's an EGR
position sensor to verify that its working. So disconnecting anything
brings up the Check Engine light and a trouble code.
To get around the computer, I made a metal plate which matched the outline
of the EGR valve gasket and installed it with the gasket. The EGR position
sensor reports that the EGR is working and no error codes!
Why block off the EGR? It recirculates the exhaust gas back into the intake
manifold to reduce NOx emissions. Ideally, you want the coolest air in the
intake, the EGR adds extremely HOT exhaust gas in. And it screws up your
fuel/air mixture - rather than clean outside air, you have hot CO gas
coming back in. The result is less power and poorer gas mileage.
Blocking off my EGR valve increased my overall hp (every little bit counts
on a 2.3l ford) and increased my gas mileage by 20% around town.
At least on the '95, the ECU command to the EGR control valve and if it
doesn't "see" the expected manifold pressure change, sets the check
engine light. As for "blocking" it off, well the purpose is to reduce
the amount of "excess o2" and reduce combustion chamber temperatures to
preclude the formation of NOX, during specific operating conditions
(primarily LOW output levels, meaning cruise and small throttle
openings) Visualize not very much fuel being injected to need available
oxygen. So they replace some of the pumped volume with a gas that has
the oxygen removed. Cooling the intake charge is good for maximizing the
amount of oxygen available for WOT conditions, but please tell me how
much time you spend there!!! If blocking off the recirculation resulted
a 20% increase, I would surmise there was a lot more "broken" and not
functioning on that Ford than just the EGR valve controls. Given CAFE
fines, I doubt the manufacturer is going to "give up" 20% gas mileage to
reduce NOX emission with an EGR valve.
Eugene Blanchard wrote:
Since my LT-4 doesn't have an EGR valve because of additional cam overlap
I'm assuming the valve is supposed to close when rpm/throttle increases
(vacuum decreases, or should I say manifold pressure goes up), so it's
'active' only with little or no throttle. And since the ECU controls the
mixture thinking the EGR is working I'm wondering if the mixture will be
richer because of the blockoff (instead of just a cooler charge) --
enriching mixture is usually a good thing for power and throttle off/on
transition with these newer cars that run so lean, and more power means less
throttle at any given power setting so mileage would go up a little maybe.
But what about carbonizing the cat. over time because of the richer mixture?
Maybe the fix will cause an expensive repair later on if the cats. are left
in place and block up?
Just a thought...
'96 LT-4 CE
Hmmm.... "badly stuck" can have two very different meanings:
The 1990 Vette has a basic negative backpressure EGR valve. It doesen't have
an electrical connection, so the ECU cannot directly determine if it is
functioning. The ECU calculates EGR functionality based on changes in sensor
output (knock and O2) when it "expects" the EGR to turn on/off. If it
doesen't see the change it expects, it will set a code 32 (EGR circuit). If
the EGR is stuck open, it will most likely set a code 45 (Rich exhaust). A
stuck-open EGR will reduce oxygen content in the combustion chamber at all
times though, resulting in poor performance (especially at idle).
Stuck open = runs bad, code 45 present, CAT damage possible
Stuck closed = runs well, no code 45, CAT damage doubtful
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