Re: fuel economy theory

[Night Shadow <soltwede@ucsub.colorado.edu>]

Also, couldn't a blocked charcoal canister cause problems like this? Now
that he has pulled all the holes?

Eric

80 Rocco (Daily Driver)
81 Rocco S (2.0 16v swap and restore in progress)

"For Aquarians, the physics of loopholes is a perfectly valid science." 
-Kelli Fox

On Thu, 17 Feb 2000, Ian Overholt wrote:

> How about this theory?  Your mixture was adjusted on the rich side to 
> compensate for the vacuum leak.  Now that you've plugged the vacuum leak, 
> you are running too rich and are getting poor mileage.  Do you see a lot of 
> carbon on the back of your car?  Blackish smoke?  I would just take the car 
> to a mechanic who can adjust the mixture while checking the CO.  If you 
> continue to run too rich, your cat will not last very long.
> 
> Ian Overholt
> '88 16v
> '78 Champagne Edition
> 
> 
> ----Original Message Follows----
> From: Oliver Seiler <oseiler@acm.org>
> 
> My theory is that the ECU thinks the engine is
> running lean (dead oxygen sensor) so it tries to richen the mixture. With
> the vacuum leaks, however, air flow through the air flow sensor would be
> reduced, meaning that the extra fuel the ECU is trying to provide
> (changing the duty cycle on the frequency valve) isn't actually getting to
> the injectors, so it sort of balances itself out (in my case, the mileage
> was around 19 MPG before I started mucking about). Plugging the vacuum
> leaks increases air flow through the sensor, which increases the amount of
> fuel to the injectors, which causes my mileage to get worse. I wonder if a
> previous owner just started unplugging things until he passed emissions
> tests...
> 
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