O2 sensors changed on 1991 lincoln cont. but still poor mileage! Why???

its a HUGE car 8-cylinder? we're you expecting 20mpg?

OK first it is a V6 3.8L the Conti had only a 3.8 from 88 to 94. it is not huge.
second when did u tune it up?
Do not use Platinum Plugs.
Have u tried fuel injector cleaner?
l suggest Seafoam u can get it at most auto parts stores.
Take the car to Advance & have the Codes read, they do it for free then post ur information & get the best answer u will find on the internet.

PS l own two Lincoln Continentals of this vintage & l get 18 city & 24 highway every day all day.

in addition to what Steve stated make sure you change the air filter make sure its shifting into overdrive do a complete tune up wires and coils because they get weak over time. Also new injectors are not that expensive so if the injector cleaner does not help replace the injectors. Be sure to disconnect battery during the tuneup that will reset the computer.

try and have the injectors flushed

You really want to increase this car is gas mileage & performance. You can save money at the same time. This is done by adding a new fuel reformulator that was just released to the US public a few weeks ago after being tied up in govt. regulations for 10 years. You add a small amount of this formula to ur gas tank every time that u buy gas. It increases ur gas mileage by 7% to 19%. If u do the math, any mileage increase over 4% saves money in ur pocket. It also makes older cars run better. The stuff has been tested by FOX News & NBC News affiliates. Check it out at http://saveongasoline.biz . Make sure u click on the MOVIES Tab to see the news reports. You can also get paid for sharing this news with others. Use the money that u make to buy a new hybrid car. Got more questions? boatclubgo.com Subject: = save gas