94 Taurus 3.0 runs fine, lousy mileage

Anyone have ideas where to start diagnosing the cause of low mileage? I'm getting well under 20 mpg with a 94 Taurus 3.0 wagon that runs fine, idles beautifully, starts every time, and drives straight and
true.
60% in-town, 40% 65 mph highway driving.
-- EEC-IV code reader returns 1-1-1 (no problems) -- D"O" is selected on the AT, and overdrive is definitely working -- Moderate driver, no accelerator punching -- ok, not often, anyway -- Regular gas, no pinging and no mpg change if I go to higher grades -- Tires at recommnded inflation (Goodyear Aquatread -- but mileage sucked before putting them on) -- AT AXOD-E has usual '94 troubles (when warm, occasional slam shift at slow down followed immediately by speed-up -- such as a Yield sign or a turnpike tool booth -- and occasional shudder) -- No obvious gas leaks at tank or engine and no raw gas smell -- Litte or no chance that gas is being siphoned by local teen-age Moped riders
Any ideas where to look?
Dave G.
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Dave G wrote:

Change your VSS sensor and see if it helps.

Try new plugs and wires if you have not done so. Check all the little vacuum hoses under the hood for leaks. Change the fuel filter and run a few cans
of injector cleaner though it. Take off the air plenum hose and look at the MAF sensor to see if its dirty or has crud on it.
YOu did not state specifically how bad your mileage was. I think our wagon Ave. 16/18 in town. Its got as high as 29 MPG on the road under optimum conditions. 20 may not be far off if you d a lot of city driving.
BOB
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Dave G opined in

I would start by looking at the timing. Borrow a timing light and set to 12 deg (factory is 10) with spout disconnected. Keep advancing till it shows a ping then decrease by one. Occasional ping is okay. Remember to reconnect spout.
Other factors: How many cold starts do you make a day? Miles per cold start EGR function/flow... it's basically working or you'd have a code. But are the passges clear?
Last, Gasoline brand. I use Speedway exclusively and get 22.5 60/40 Hwy/ suburbs/many starts in a 3.8 Bird 150mil/day, and 26 in 95 3.0 Taurus 90/10 Hwy/suburb few starts 100mil/day.
Knock off two mpg for the wagon. What is the NET weight.. do you carry a lot in it?
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What is the actual fuel mileage and how did you check it?

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Generally, I keep receipts of gas sales for quantity, recording mileage, then zero out the trip odometer with each fill-up.
Actually -- working from Bob Urz's and Backyard Mechanic's replies (thanks), I need to check the MAF. And I need to begin recording it afresh. I just cleared up an EGR issue (nipple broken off solenoid/control valve, gummy EGR and malfunctionion ERG sensor, all 3 replaced).
Dave G.

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So what is the actual fuel mileage?
wrote:

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Dunno, yet (starting afresh). I should be back in a month or so.
Dave G

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Dave G opined in

See... now you see the value of providing ALL info!
WHILE the EGR system was going bad, the fuel map probably got ALL screwed up.
Did you reset the PCM by disconnecting battery for a half hour? IIRC, you could have reset the codes by doing readout but NOT the mapping during open loop (warmup, WOT) operation. Thomas will correct me if I'm wrong.
Once everything is fixed, you should always do a reset.
If you dont have pinging, probably is NOT the MAF.. dirty ones typically run lean.
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Of course, it helps to know everything that's relevant... :)
As for reset -- I disconnected the battery during the EGR sensor replacement, but probably not for half an hour. Even with my 10 thumbs, it couldn't have taken that long to pop off one tiny hose, one electrical connector, and wedge the old sensor up and out of its spring holder, then reverse with new sensor.
Battery disconnect during the solenoid / control replacement was a lot longer, but the Check Engine light still yapped at me, because I had not yet replaced the sensor. That solenoid would most easily be changed either by removing the engine or training a small monkey whose arms had been broken in two places...
I also used my hand code reader per its instructions to reset the codes after sensor replacement -- with my model, you flip from TEST to HOLD while the computer is sending initial rapid pulses during key on, engine off testing -- I don't know from reading / mapping / open loop / warmup / wide-open throttle operation. Wouldn't the latter damage the engine?
Dave G.
On Mon, 17 Nov 2003 00:05:36 GMT, Backyard Mechanic

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Dave G opined in

Sounds like you covered that then
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Sounds like Dave G got everything covered. I used to have a '94 Taurus GL and the mileage was a little above average. I used to get up to 22 city mpg and 27 highway mpg by using Exxon/Mobil fuel. I now drive an '02 Ford Taurus SEL Premnium and it runs very good. I switched to Shell fuel and I get up to 32 mpg on the highway and about 24 city mpg. That is above average.
Exxon/Mobil are good fuel and are not the best. They burn a lot of gas in your car. Sunoco fuel is pretty good, you save a little gas in your car than using Exxon/Mobil fuel. Shell fuel is probably one of the best brand name fuel on the market. They really do save a lot of gas in your car. Independent fuel companies such as Speedway, Paciffic, Flying J and etc. are pretty good. We don't have that many independent fuel franchise in Vermont.
~CyberWolf
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Things that can affect MPG on an otherwise good running car.
Fuel makeup
aerodynamic drag
gearing
tranny slipping
amount of weight in car.
city driving
driver with a lead foot or excessive idling
tire design
wrong size tires on car affecting odometer / speedometer
speedometer gear and / or circuit
A/C on all the time
plugged exhaust (cat converter) or intake filter
low compression
brake drag
high speed driving (driving significantly over interstate speeds when car is optimized for lower speeds)
ignition and/or cam/valve timing
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You forgot cooling issues. My '92 SHO ran rich to compensate for higher operating temps until I replaced the radiator. I'm still not getting the 26-28mpg that other SHO owners say they get and my driving is conservative compared to some of them.
JD

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What are the different tire options (low cost, medium and high) that make the 94 Taurus wagon run smoother?
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I don't pick tires for smoothness. I usually look for handling tires. Some tire manufacturers use compounds and tread designs that they claim will improve mpg. Michelin claims this for their rubber compounds for some models. Cooper user to sell a narrow high pressure (40 psi) radial that they said enhanced MPG. For these tradeoffs I doubt they would be smooth running tires Look at tires websites for detailed information
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