fumanchu

i have a 1998 t100. i have only owned it for one tank of gas, but it only got 12mpg. it has 16 in tires, and 15 are stock. any ideas on what may be wrong or how to get better mileage. or any after market parts that will help. i'd prefer to leave the bigger tires, but will go down to 15s.

250000_yota

There are a few real simple things you should be doing.

1) keep your foot out of the skinny. My '98 is lifted, geared and supercharged, and I still pull 17 out of it.

2) maintenance. Give it a good tune up, with quality, Toyota parts. Toyotas don't like the other stuff like Bosch and delco and champion. Factory denso or NGK only. Keep yr air filter clean, and while your near it, clean the mass air flow sensor with specific mass air flow cleaner. This sensor measures how much air and at what temperature, the air is entering the engine. It's critical to keeping the air fuel ratio within spec, so if it's dirty, it's not reading acuratly. Keep the tires in good condition, rotated and inflated. I usually keep mine between 35-40 psi.

Now as far as 12 miles to the gallon, that is bad. Is there a check engine light on? Does it seem to be running rough, or idle high or rough, does it hesitate when you leave a stop light?

fumanchu

thank you! when you say tune up, what exactly do you do to yours? and there is no check engine light or any of the other things you mentioned. but, it does idle weird, slowly goes higher, then back down.

BamZipPow

Um...hopefully yer tires aren't 16" tall.

I'm guessing yer saying yer rims are 16" but that doesn't tell us anything about what size yer tires are. It should be on the sidewall and should look something like 135/75R-15. Post up yer tire size, please.

When I got my used 1998 T-100 and got 15mpg on the highway. When I got home, I immediately cleaned the MAF and reset the ECU (pull the EFI fuse located in the driver's kick panel fer about 2-3 minutes). I got 18mpg highway on the trip back. I did a tune up and got closer to 21mpg highway a few weeks later.

My best is 35mpg at 65mph with all my aero mods.

Shoot some video of yer idle problem and post it.

fumanchu

they're 16" rims haha. and what do you do for your tune up? i bought spark plugs, fuel, and air filters, and MAF cleaner. anything else that you would do? and when you pull the EFI fuse, is the truck running?

BamZipPow

No...the truck isn't running nor is the key in the ignition. Just pull the EFI fuse out fer about 2-3 minutes and replace.

What kind of spark plugs did you git? I would only recommend the NGK or Denso dual grounded plugs as anything else seems to have problems with Toyota engines/ECU.

The only other thing I would take a shot at is pulling the throttle body off and give it a thorough cleaning. Pulling the IAC valve off and completely cleaning that would be a bonus as well. You can git a new IAC valve gasket at O'Reilly's Auto Parts fer about $5 or so. Make sure you bring in yer old one as they have been known to give you the wrong part.

You might also look at checking/cleaning/replacing yer PCV valve, too.

BTW...what is yer tire size?