33 miles to the gallon down to 18

I have a well maintained 2002 Focus with 44k miles. We were averaging 33 miles to the gallon and over the past year it has dropped down to 18. I have replaced the fuel filter and the sparks plugs. The air filter is clean. I have switched gas brands and ran fuel injector through it. The milages actually dropped by about 4 mpg after I did all of these things. I have ran about 1500 miles since doing all of this and the gas milage has not increased. There are no warning lights on and the car seems to run and idle fine. Any ideas of what is wrong?

I've had the same exact problem.
someone suggested the cold weather is doing it but I dont put much stock into it.

So I'm not the only one with this problem. Twice in the dealer and they say that there's nothing wrong with it, some milage variance is to be expected and then basically told me I'm retarded and I should stop sweating the small things. For anyone in MN, DONT GO TO TOUSLEY!!!!!!!!!!!!!! I should fire bomb it and say fix it all under warranty b%*ches!!!

Also a mechanic in the city I work for said a sensor could be stuck in one position which makes sense, but tousley said that would trip the computer, they all lie. So anyone get this fixed yet?

still nada
i have an intermitant EGR error though.

I've been thinking of pulling out the TPS, MAF, and O2 sensors and 'fixing' them myself, then the dealer would have to replace them and that could solve the problem. I guess I'll try new plugs and replace the LIFETIME air filter, lol.

pull your intake you may have a carbon clog.

Me? I ain't pullingThe dealer called and said they put it on a bench and track the wheels revolutions and says it makes 30mpg. But I say there's NO HEADWIND IN THE GARAGE!! Anyone know about that test, would it be similar to a dyno where the drum is dynamic and changes?

I know this is going to sound dumb, but try replacing the thermostat. That would be the most logical thing that would not trip a service engine light. For instance if your coolant is not reaching the correct operating temperature then it will cause the engines operating program to think engine is cold and will adjust fuel accordingly. Like I said it seems dumb, but it is fact. Remember years ago when people used to replace thermostat every year as maintenance? They have made most of them hard to replace nowadays and most people do not replace on regular basis any more.

That doesn't sound silly, in fact that makes more sense than anything I've heard from ford. Plus it's a $10 fix.

Kinda my thought, and the way I like to proceed into the unknown in my shop. When in doubt, start with the cheap and work forward.

anyone have any luck with this at all? I have an 2004 zx5 2.3L model and the exact same thing has happened to me this past year. And it was happening over the summer too so i don't think weather is affecting it much. i don't know a whole lot about cars so if anyone made any progress with this please let me know. Thanks.

Actually i agree that is not dumb.  If the thermostat is stuck open the engine runs to cold making the fuel dump faster to keep the car running.  That will be one reason for poor gas mileage.

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ORIGINAL: wheelsup68

I know this is going to sound dumb, but try replacing the thermostat. That would be the most logical thing that would not trip a service engine light. For instance if your coolant is not reaching the correct operating temperature then it will cause the engines operating program to think engine is cold and will adjust fuel accordingly. Like I said it seems dumb, but it is fact. Remember years ago when people used to replace thermostat every year as maintenance? They have made most of them hard to replace nowadays and most people do not replace on regular basis any more.

I just wanted to see if any of you guys with this bad gas milage problem ever figured anything out with it????One suggestion I had for the guy that originally started this thread he said the gas milage actually went down 4 miles to the gallon after replaceing plugs and filter I was just wondering is there anyway you guys may have changed your own plugs and didnt double check the gap before installing them. I know alot of the plugs people buy today are pre gapped supposedly but Id never trust them right out the box,, not unless you want 4 at .040 and 2 at .065 I have personally had them this far off  new fresh out the box and they were supposed to be pre gapped ready to install...just a suggestion i figured id throw out there. Also with the thermostat theory are you guys saying with newer cars it makes a difference rather the thermostat is stuck open or somthing? I just wanted to point out that I have had numerous old and new cars and trucks that i have just taking the thermostats out all together and it made no difference on gas milage,,The biggest thing i think ever happend with a thermostat out of the car all together was i forgot to reinstall before it got really cold one year and it took forever to get some heat going but other then that engine ran fine and gas milage never was effected. On my V-8 engines and truck engines im sure i would have noticed almost a  50% reduction in fuel economy when i took the thermostats out.

I have had the same problem on my 02 focus, with exactly 45k miles on it!!! I do notice that my throttle position sensor is failing, because when i put it in neutral(its auto) the and revv it, the rpms wont drop under 3000rpms, unless its put into gear(not a good idea) or if you let it take its time, which can be from 30 seconds to 2 minutes... its ANNOYING and the dealer says theres nothing wrong... IDK... but i get an average of 17-22  mpg depending on how heavy my foot is!

This has me confused but all I know is Id be pissed if I were  focus owner!! I have seen guys conplaining on the explorer forums about only getting about 15 miles to the gallon, but those are 4.0L engines in 4 wheel drive suv,weighing probably twice the weight of your cars. well I hope someone figures this out,,, sounds like alot of you guys would benefit from it....