Bump, Please help.

 

So at 200-210 miles, your on empty? With all of your new parts, I'm not quite sure what to say. Do you get any black smoke out the tailpipe? That's pretty rich, I'm not sure if a malfunctioning fuel pressure regulator would cause bad gas mileage. Maybe your converter but you said your car runs great. Have you had your car checked for any DTC's?

 

How are you calculating your MPG? You need to divide miles driven by the amount of fuel used, not the amount the tank holds. If you have been refilling at 1/4 tank and performing the calculation wrong you could be closer to 30 MPG. If you're driving close to 70 MPH in winter with the defroster on the whole time, that would be normal.

 

Sorry if I missed it, but what tranny?

-Rand

 

It is a 3 speed automatic. And i fill up completely. Reset my trip meter. Then drive the full tank to as close to empty as "comfortable" Since im not sure if there is a gas light on these cars. Then i take the 210 miles and divide it by 10 gallons of gas i put into it.

21 mpg. ..I have yet to fill up completely after putting in a new air filter and doing the 02 sensor so. Maybe that will help.

 

Have you checked tire pressure?
Are you using the front defroster? (it uses the AC compressor to get rid of the humidty, and will hurt gas milage)
Have you cleaned the inside of the car? The more your hold, the less your milage. (not the cause of that much milage loss)
Has your PCV valve been changed, or is it blocked?
Are you letting your car idle to warm up for a long time?

I think the 98's may have a MAP. in my 01, I replaced my MAF, and my gas milage skyrocketed.

Just some thoughts, hope this helps!

 

fueleconomy.gov reports a 1998 prizm 3 speed at 24 city, 30 highway. I'm sure you knew that.

I don't know what to say other than checking the basics: tire pressure, fuel sensor data, rich lean ratio, gas leak?

-Rand

 

I'll echo what others have said. How fast are you driving? How is your tire pressure? Are you cranking the defrost? (The defroster lowers your FE the same amount on low as it does on high - the compressor is either on or off, the fan speed is different.)

 

I drive like a granny around town, slow starts. No leadfoot for me. On my commute i usually stay at 70-75 mph. Wish i had cruise control Since i got the car the engine quieted down alot after normal tuneup and just driving it period. Tire pressure is good. Just bought 4 brand new winter tires. Defrost i was using for a while i will stop that now. Im at 140 miles now and just a hair below half a tank. So thats already an improvement. Ill see where i am after the 70 miles of driving tommorow.

Thanks for all your help guys. Appreciated.

 

A 3-speed is going to suck FE-wise going 70-75 mph. There's no way around it. Third gear simply isn't tall enough to yield great FE. New tires take a good while to break in. Winter tires typically aren't great for FE either.

One other thing to try is to unhook the battery for a while to fully reset the ECM. Just like with PC's - if in doubt, reboot.

 

My corolla gets around 20MPG. believe me its not fun paying 30$ per week just to get around. Since my vehicle is suppose to get around 26MPG city and around 32highway. If i go on highways it still gets around 38MPG but on local roads I get 20mpg go figure ...

 

Latest update. I got 250 miles out of a tank of mixed city/highway driving. Probably could have gone to 270 but didnt want to push it. I think thats my max ill get for this car honestly. Thanks for all your help guys. I appreciate it alot.

 

changed from the Tahoe to a prizm for gas mileage? not what you expected, eh?

don't worry...I had a 4-cyl 4x4 Tacoma that got ~18-20mpg (as high as 24mpg highway) in the summer, then 15-17mpg in the winter, and switched to a corolla after mine got bought back, and I sort of miss my truck too

I'll give the corolla/prism some credit though: they're light, peppy, and ride relatively nicely compared to trucks though :thumbsup:

but back to business:

don't forget this is winter time:
1.) cold air is dense air with more oxygen; and to ensure the proper air to fuel ratio is going into the engine, the car will add more gas to the increased oxygen
2.) gas companies will use additives to prevent the gas from freezing; it also lowers your gas mileage
3.) tire pressures (which looks like you already checked) lowers with colder temperatures; make sure you check that tire pressure cold and increase it to compensate for the cold weather if necessary. I brought all of mine up to 30psi and I raised my gas mileage up ~10%
4.) I'm not sure if you do this, but extended warm up times will slightly lower gas mileage
5.) snow tires, with their meaty tread pattern, can also reduce gas mileage compared to slick/smooth all-season tires

with that being said, I also live in MA with a 4-speed auto, and this winter am only seeing ~27mpg for mixed driving, and for a highway trip back from NY, only saw 33mpg. On the other hand I saw 38mpg on an highway trip last summer, so it just goes to show that winter time can reduce your mpg enough.

 

Iv been wondering the same thing..... im a delivery driver and i monitor my gas mileage all the time....... the prizm should have close to a 13 -12 gal tank. if your topping your tank off at around 10 gal then you should have 2 or 3 gals hidden around that E ... XP

My mileage has really been all over the board... iv had 210 miles out of a tank and there has been times i can get 280. 1 thing i know for sure (for my case) is that driving highway will suck more gas then you think so i try to stay on the roads and since then, my mileage has gotten better.

i think these 3 speed auto prizms are better street cars then highway cars which is unique.

May i higher recommend that you keep a very close eye on your oil levels since your on the highway doing 70 so much.

 

Good input Fox, Thanks. Do these cars have a gas light to warn when your real close? Im real weary on driving it right down under the E mark. Going from my tahoe it was just like. Once it hit e you better find some gas or your screwed.

Also, I think my car gets much better mileage on the highway. I travel 70 miles a day and my gauge wont move at all from full the whole time, Once i get on backroads. Thats when i notice it goes down. Also, After letting my car sit the night, i get in it. And look at the fuel gauge to see that i dropped almost a quarter a tank from when i shut it off. Then when ii start driving it goes back up? Wierd.

Im at 140 miles right now and still half a tank left. I may try driving a little past the E this time.I will for sure keep an eye on my oil, Thank you much.

 

yes there is a low fuel light thats right next to the check engine & rear defrost light. there is no low oil light tho so take a look at your dip stick every 1k to make sure your not lossing to much oil. i lose 1qt every 2.5k so im one of the lucky ones (for now)

Iv ran my tank down to where the needle was on the E its self so there is some hidden gas there.... altho one should indeed always be careful when driving close to E..... the fuel gauge will read differently when you let the car sit over night because the fuel settles and calms. when the cars moving.... the fuel is moving around making mini waves in the tank showing you that there is more fuel then when it sits over night. you will notice the fuel reading is different also when you have the car parked at an angle (like on a hill) its nothing to really worry about.

 

CORRECTION............. once the needle is on the last line close to the E... you got 1 gal left in the tank

 

You've got about 2 gallons left when the low fuel light comes on. My fuel light doesn't come on until my needle is noticeably past E, and I've never put in more than 11 and a half gallons into it at once.

 

Shawn5800: Your never going to get an accurate reading that way. Post #4 is the right way to do it. Anything else is guesstimation.

 

Have you checked for any exhaust leaks at all? I had an 05 1zz supercharged Corolla and even mashing the pedal all day and doing city driving I could still get over 21mpg.

Also to confirm what everyone else has been saying you take the amount of gallons of gas you fill your tank up with and divide that by how many miles you get throughout that fill up. Even this is still a bit of an estimate but you still are getting pretty close and accurate results

 

After changing my air filter, and replacing the bad 02 sensor. Upstream. I ran my last tank of gas down until the light came on, and filled up completely. Reset my trip. And i got 294.5 miles!!!!! Wooohooo! Record. That sensor must have really been hindering performance

 

The upstream sensor is definitely a big determinant of gas mileage. I thought your original post said you had already changed the oxygen sensor. What's the story behind that? Was the new one bad? What brands were you using?

 

Another thing... as mentioned before driving 70-75 miles per hours will eat up gas.

 

thats the same observation i have made...... i believe this is more of a auto 3 speed issue tho.

 

Maybe you have a damaged sensor or something? Looks like your car may have been wrecked, the headlights look "too nice" haha. I have owned a couple Corollas w/ the 3 speed auto, and the mpg was much better than 20. I was getting about 27mpg with those. I just picked up a 99 Prizm with the 5 speed stick. Funny, I owned an almost identical car several years ago. That one was an LSi with all the goodies and still stick shift! This one is base model, but at least it has A/C... My last Prizm had 218k on the original engine when my girlfriend crashed it, and it was still pulling over 30mpg at 80mph freeway. Sweet little cars. My new one only has 85k miles on it, so it has a ways to go.
(pics to come soon)

 

Actually, it was in a small accident haha, It got clipped in the front. So there was a new bumper installed and new headlights and corners. Along with the jackass that owned it before me never watched the oil level and blew the engine. So there is also a newer engine in it. I bought it for $500, now have $800 into it and it runs like a champ honestly. I love this car, I never thought i would make the transition from my truck but. Driving this is fun, it holds the road nicely, and the mpg is just amazing now. Last tank i just got 310 miles out of it. Im amazed at this little car. That is with doing 70-75 mph all the time basically.

I think im starting to love this car more than my truck...Less headache, more fun, better mpg. Great car overall. Best of all, Its paid for! Kudos to the person who designed this simple 4 cyl car. Great job.

Also, as for the 02 sensor. It was bad when i first got it, when it had the bad sensor in it i was barely getting 21 mpg. Highway. Now after replacing it with a $90 Bosch sensor and a brand new air filter. Im consistent at 290-310 miles a tank. Amazing little car. Only thing i dont like is how loud it is at over 70mph. Otherwise. My favorite car by far.

Also, i will be buying two performance tires for the front this spring, Taking my winters off. I cant wait to see how the handling and everything improves. Anyone know how to fix a damn air leak in a door My passenger door whistles like crazy at anything over 50 mph.

 

Sweet!! You got a hell of a deal on the car! Glad to see your mpg is so good now. What did you think made the big difference? The o2 sensor?
You should probably have a matching set of 4 tires for safe handling reasons.
My girlfriend's Corolla used to whistle really bad on the freeway, and even let a little water leak in driving in the rain. We bought a door weatherstrip rubber thing from the dealer (sorry I don't remember the exact term they use) and it simply clipped right in, all the way around the door. Took care of the noise immediately. Around the door, you can see the old rubber has little clips that hold it in to the door, just pry them loose, and take the old rubber off. I let the new one sit in the sun for an hour or so to soften it and make things easier before I clipped it in.

 

The 02 definitely made the big difference, but im sure getting rid of the mice infested air filter helped also, And sucking the leaves and acorns out of the air box with a shop vac. Damn rodents.

Thanks for the info on the weatherstripping! I may try some of the stuff i use around the house here. Its just stickied on, i may use it to fill in any gaps. Thanks again!

 

I have some of that stuff, too. Might not look perfect, but might work just fine! Have you run Seafoam through your brake booster hose? I'm going to probably tomorrow. My last Corolla ran much, much smoother after I did it. So did my Honda CR-V. I log mileage each tank, too, and noticed about a 1mpg gain on the Corolla overall after Seafoam, and about 1.5mpg gain overall in the CR-V. Worth the $9 to me. Auto repair shops charge about $90 for a fuel injection system cleaning, and you can do the same thing at home if you 're patient! I normally run a can of Berryman B12 through the tank every other oil change, too. My highest mpg on a tank on my last 99 Prizm was 37.5mpg coming back from Phoenix, doing 75mph with tha A/C cranked! That may have had something to do with Arizona gas being different formulation than the crap they give us here in California....