Bad Gas Mileage

I had been getting really good gas mileage on my 94 Ford Escort. I was getting anywhere from 30 to 32 now all of the sudden I only get about 21 to 22 mpg.

Work I have had done in the past month has been:

Tune up
Oil change
Had lower ball joint replaced (Front, right side)
Brake hose replaced and repair the CV Axel.

I don't know if any of that would make a difference but just thought I'd tell you all I have had done to the car in the past month to help me find out why all of the sudden Im getting worse gas mileage.

Any suggestions why and what I can do to get my mileage back up there? With gas prices like they are I need all the help I can get.

Thanks in advance!

Welcome to AF!!

The usual culprit is a bad O2 sensor. Usually the upstream sensor. This is located in the exhaust system before the converter. This measures the amount of Oxygen in the exhaust leaving the engine. If it is bad it will cause the car to use too much fuel and thereby decrease your fuel mileage. If both sensors are the same age I would replace both the one before and after the converter. Good Luck!

Compression test on all four cylinders.
Gasket usually fails on fourth cylinder, front-right side.
In addition head may crack on exhaust side, 2nd and 3rd cylinders.
Differences in the way the iron block and aluminum head expand and contract when heated/cooled cause or contribute to the issue.
Head is repairable for around $150-300. If the problem, make sure you take it to someone with a good reputation and will repair/test it right. (check with the racing crowd)

Another possibility is timing belt slip which is determined by checking the timing marks.

Third possibility will probably be evident in the fact that the vehicle takes an extended amount of time to heat up. But a thermostat/coolant bypass valve in the "water outlet" may be permanently open and cause the engine to run cold; or well below normal operating temperature.

Mileage drop after the tune up. Sounds like a tune DOWN. What did they do? O2 sensor. Maybe. Quick and dirty..give it a Seafoam clean out and run some hi test cleaner type gas. Next I would try and find someone that can maybe remove and clean the ends of the sensors. This can/has been done. Getting them out requires a special wrench. No fun. Aftermarket sensors are much cheaper..and known for problems. Some places..understandably won't use them..or aftermarket cats.

By the way those automatic shift trans, at least around here, typically give out between 100 and 130k miles. If it's shifting funny, missing 4th gear or the torque converter isn't locking, that will drastically cut mileage as well.

I notice you had the brake hose replaced and a restricted hose will cause the brakes to drag and will ruin your mileage. Check the other hoses for bulges. While you've got it up in the air spin all the wheels to make sure none are dragging. If the front end is way out of alignment it will cause tire drag. Check the front tires for wear on the inside or outside. IF the outside is worn there is too much toe out, Conversely if the inside of both tires are worn there is too much toe in. Camber or caster will not affect tire drag unless it is way out of specs. You can tell pretty much that the toe in is right just by putting the steering wheel straight ahead and visually lining up the front wheel with the rear wheel. If it is out enough to cause mileage problems you will be able to see it.