need help with gas hog 2000 corolla.

[byteme2]

Hi everyone,
need your expertise on this. i helped out my niece by changing the engine oil, transmission oil and filter, spark plugs (denso irdium plug), serpentine belt (gator brand) and the belt tensioner. i thought this would give the car better gas consumtion. everything went fine. a week later, she complaint to me that the car waste gas like crazy. she had to fill twice this week. where she used to just fill once. i test drove the car for about 6-7 miles and can actually see the gas needle moved about 1/8 inch. this car used to be very gas economical.
i checked and cant see nor smell any gas leakage. spark plugs were pre-gap correctly.
what should i check to remedy this problem?

[w203]

shes running rich

did u change the air filter?

fuel pump/filter okay?

[FinalGear]

rotate those tires.....plus it sounds right.....I fill it up just as much (I travel a lot)....

[byteme2]

air filter was also changed. i can't believe that the car could waste that much gas.
but what i dont undestand is how can it changed so much from before and after the work was done...

[byteme2]

from my calculation, the car now runs about 12+ mpg. 1/4 tank for 40 miles. full tank is roughly 13-14 gal. 1/4 tank is 3.25-3.50 gal. 40 / 3.25 = 12+ mpg.
what have i done to the car?

[4runnerracer]

Try going back to the old spark plugs or use OEM ones and see if your MPG improves.

[FinalGear]

I think its the person who drives the car.....heavy feet...

[mikered30]

Any check engine codes? Could be an O2 sensor. I will ask the obvious, is there a fuel leak?

[costadragon220]

Originally Posted by FinalGear

I think its the person who drives the car.....heavy feet...

I concur. I think heavy foot syndrome.

Probable faulty gauge or gas level thingy .... *brain fart* ....

[byteme2]

imposible - she drives like an old lady..she is only 24 and her top speed on the freeway is 55. i told her that she drives like an old lady and she was mad at me.
anyway. old spark plugs already in the trash week ago. i think going with OEM spark plugs is a great idea..
Can an O2 sensor be bad and cause this problem? or the cat converter

[darcsyde]

yep bad 02 and cat can cause the gas miles to go down. Clean out the intake manifold, run some fuel system cleaner through the gas tank. Make sure tires properly inflated, rotated, balanced. Get an front-end alignment done.

just a few suggestions

[FinalGear]

Originally Posted by byteme2

imposible - she drives like an old lady..she is only 24 and her top speed on the freeway is 55. i told her that she drives like an old lady and she was mad at me.
anyway. old spark plugs already in the trash week ago. i think going with OEM spark plugs is a great idea..
Can an O2 sensor be bad and cause this problem? or the cat converter

Does she blast her AC/Heater all the TIME?

[w203]

odd, if the problem wasn't there before but is there afterwards i suspect its something you've done. what parts did you use? can you list them?

12mpg is exotic territory, i could have floored my 1zz and still manage to get above 25mpg

[byteme2]

i took the car to Az this morning. it found code P0420. from researching this forum, i am going to order the Pre cat O2 sensor. if that does not solve the problem, i will replace the cat. i dont know why the CEL does not show..maybe the bulb is bad?
took the car to Costo to have the tires change but the waiting time was like 4 hrs long..Anyone has any experience with BFG premier touring tires?

[Buurin]

2000 Corollas use iridium plugs from the factory. Both Denso and NGK (BKR5EIX I think) are factory spec'd.

From what I read elsewhere when troubleshooting P0420 there's usually more to just replacing the O2 sensor.

Ya, last time I floored my car I got 27MPG, and that's on a 99 without the benefit of VVT-i.