1989 A90Q gas mileage
audi at humanspeakers.com
Thu Jul 13 16:35:53 EDT 2006
> I had some work done on the engine and the car ran really well. The
> mechanic asked me to bring it back in to have the oil changed and "set" the
> engine. Ever since this was done. my gas mileage is awful. I'm lucky if I
> can get 425 Kilometers from 50 liters of highest premium gas.
I assume you were measuring fuel economy when it was "running great"
before the "adjustment"? Does it still "run great"?
Excuse me while I translate for myself...
425 * 0.621 = 264 miles
50 * 0.264 = 13.2 gallons
so, 20 mpg in medieval units.
> Any suggestions on what might cause such poor gas mileage suddenly? I can
> smell the exhaust when I start the car and stand about 8 feet away from the
Well, 20 mpg isn't *awful*, but the car should do better. Something is
wrong... as long as the "adjustments" were within "ECU correctable"
range, the engine should be running fairly efficiently whenever it's
warm, if all the devices are working correctly.
If all is working and the adjustments were done properly, I'd expect
23-26 mpg (based on experience with my US model), or about 20-25% better
than you report.
So... you might have vacuum leaks, malfunctioning sensors or senders, or
gross misadjustment. I'd suspect the former two being causes and the
latter being a result.
The exhaust smell (do you mean unburnt fuel?) when cold might mean
things are set way too rich, perhaps even too rich for the ECU to
compensate when in closed loop (warmed up engine).
If you can, it's time to measure things like OXS output voltage when
warm, ECU NTC sender resistance cold and warm, CPA current, etc.
Also check over typical "tune up" parts for age, etc. - air filter,
plugs, wires, cap and rotor, etc.
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