[V6-12v] Low Gas Mileage

[Wilfried Link]

I would add to check the plug wires. Visually inspect
the wires in absolute darkness with the engine running
-- if you see even a hint of blue spider webs running
around them, usually near the ends, you'll want to
look in to new wires. I've had Magnecor wires in my A6
for 100,000 miles, and the engine runs like a turbine.
They were also cheaper than the other sources I
considered.  A bright Audifan recommended cleaning the
MAF sensor wires. I did it, and it made a wonderous
difference in idle smoothness and off-idle throttle
response, and some betterment of gas mileage. I used
denatured alcohol and a thin cotton swab to get the
almost invisible dark residue off the wires. Just do
it carefully and very gently.  

 --- Tom Christiansen <tomchr at ee.washington.edu>
wrote:

> Nathan,
> 
> If you get the EGR code, clean the EGR passage.
> Check out Nathan White's 
> procedure for doing this.
> <http://www.mnsi.net/~natwhite/Audi/egr.htm>. 
> Nathan White uses a 7/8" flare nut wrench for the
> EGR tube connection. I 
> couldn't get a flare nut wrench on the damn thing,
> so I ended up spending 
> $$ on a set of crows feet (looks like the open end
> part of a wrench with a 
> 3/8" square for a rachet where the handle should
> be). I bought a metric set 
> and I think I ended up using a 22 mm, but I'm not
> 100 % sure of that 
> number. Anyhow... Once you get that nut loosened up
> the rest is easy. Soak 
> it in penetrating oil the night before...
> 
> You'll need a piece of wire cable for cleaning the
> EGR passage. My bicycle 
> still doesn't have a rear brake cable as a result of
> this procedure... ;-)
> 
> Remember to clear the trouble codes in the ECU once
> you're done with the 
> procedure. There are several ways of clearing the
> codes. The one that works 
> for me is to disconnect the battery. Wait a minute.
> Then reconnect it. Make 
> sure you have the radio code before doing this,
> though.
> 
> Bad news was that this procedure did not solve the
> problem for me. If you 
> after cleaning the ERG valve and passage still get
> the code, get yourself a 
> mity-vac tool and apply vacuum to the EGR valve
> (with the engine running). 
> If the RPM change as you open/close the EGR valve
> the EGR valve is working. 
> If not - clean EGR passage, tube, valve. If the
> valve doesn't hold vacuum 
> (the diaphragm is leaking) replace the valve.
> 
> If the EGR valve is working, the other options for
> causing an EGR trouble 
> code are the EGR temp sensor or the control valve.
> The temp sensor is easy 
> to test if you have an ohmmeter (or multimeter). The
> EGR temp sensor 
> connector is found in the connector bank behind the
> intake plenum (or maybe 
> it was the small bracket by the EGR valve. I think
> that was it). It's a 
> really skinny wire with a two-pin connector on it.
> The sensor itself sits 
> on the starboard, lower corner of the throttle body
> and cannot be seen from 
> the top (at least I can't see it). When you open the
> EGR valve (apply 
> vacuum) with the engine running, the resistance of
> the EGR temp sensor 
> should change quite dramatically (by at least 1-2
> order(s) of magnitude). I 
> seem to recall 200 kohm (-ish) when the EGR valve
> was closed and 2 kohm 
> with the valve open. If you don't see a change in
> resistance, the sensor is 
> bust.
> 
> If the temp sensor and EGR valve work, then the
> final option is the control 
> solenoid valve. It sits on the airbox upstream of
> the MAF sensor. Just 
> follow the EGR vacuum hose/tubing and you'll find
> it. At this point you've 
> hopefully verified that you don't have a leaky
> vacuum hose... Replace the 
> solenoid valve.
> 
> If this doesn't clear the fault, you're probably
> looking at defective 
> wiring to the ECU, defective ECU, etc.
> 
> Tom
> 
> At 07:20 AM 5/31/2005, you wrote:
> 
> >Well, I have a problem with my car. I was making a
> 100 mile trip and by a
> >calculation with an estimation of the gas levels,
> I'm achieving about half
> >of the gas mileage I should. Now, the EGR system
> still trips the check
> >engine light, it was on practically the entire time
> during that 100 mile
> >trip, I still need to get that fixed but I'm not
> sure that would cause the
> >low mileage. I talked with my dad and he says we
> might want to change the
> >spark plugs and/or wires but then he said we might
> want to just take it in
> >to be tuned up. Does anyone know something more
> specific worth checking out
> >to help narrow down the problem so I can say "I
> need this to be replaced but
> >I don't have the tools" as opposed to "it doesn't
> work good, fix now". I've
> >archived the email discussion about the EGR system
> from a few months ago
> >when I brought it up before. The car is a 1994 90
> with everyones' favorite
> >12V V6. Any help you guys can provide will be a
> great help, thanks a lot,
> >Nathan.
> >_______________________________________________
> >V6-12v mailing list
> >V6-12v at audifans.com
> >http://www.audifans.com/mailman/listinfo/v6-12v
> 
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