Basically like the subject says. In Open Loop what is the computer using to "know" how much fuel to dump in? The reason i ask is becuase I am getting bad gas milage in town. 8mpg in town, 22 on the highway. And my in town driving is for 10 min at a time going 30mph or less and only going like 2-5 miles at a time.

 

On a '95 it will take the MAF reading, go to a lookup table to relate MAF frequency to mass airflow (gpm), from this information it knows approximately how much fuel to add to reach a desired AFR, it then looks at the open loop AFR table (coolant temp vs. load) and adds enough fuel to reach the AFR listed for those conditions. The colder an engine is the richer an AFR it needs due to poor atomization.

 

At a basic level the PCM uses the MAF reading for it's calculations to arrive a injector pulse width in open loop. There are a few tables it uses to base it's formula off but the would not affect your gas milage uless someone messed with your programing. If you are having milage problems in open and closed loop I would think you have a mechanical problem some where.

Check for leaky or stuck injectors, higher than normal fuel pressures and fouled plugs.

 

Your highway milage seems about normal, especially during winter. Since your in town trips are only 10 minutes, that's hardly enough time to get the engine warmed up. A rich AFR for a cold engine, a cold A4 tranny with all its parasitic losses, probably running the defrost (AC compressor), and reformulated winter gas might just give you the kind of milage you're seeing for such short trips. How cold has it been during these drives? I would get the car on the highway every now and then to make sure the engine oil gets hot enough to vaporize all the contaminents in it.

 

Recently it has been really friggin cold, not above freezing for highs. So it seems like 8 mpg is as good as it is going to get if i'm only driving for 10 min.

 

Tell me about it... it was -10 degrees just the other morning here

You might benefit from a tune-up and the like but unless you notice something in the feel of the car, and/or your normal, warm highway milage stays in a normal range I wouldn't be too worried about problems. With only a 2-5 mile drive the engine barely gets a chance to drop into closed loop, if it's cold it will show up at the gas pump. Take it real easy on the car when cold as the valvetrain doesn't get any oil for a while, oil bypasses the filter, and other problems. I would recommend getting some longer trips in every now and then to bring oil temp up to normal operating temps and clean the cats out.

If you start noticing something more significant or the fuel milage does not return when the weather warms I would start looking for problems.