over40driv

My car is fully tuned up, all stock except BFI and new cat. conv. I drive conservative, and with the A.C. on very little. Filled up today and got 14.2 MPG. Im wondering if when I filled up before if maybe it wasnt comp. full. I seem to have to turn the filler nozzle upside down to gas-up. I have checked a year ago and got 20.

Durrr

you can try and reset the ECU and see if it does it again. If it happens again, then it would warrant further diagnostic.

sc-driver

iTrader: (7)

The way you drive, where you drive and road conditions have a HUGE effect on your miles per gallon. With 100% driving in the city, my average is usually 15-16 miles per gallon. But driving like a grandma I was able to squeeze out 18.1 mpg in just the city. It maxes out at 25mpg on the highway.

Your 20 miles per gallon seems like more highway then city, and the 14.2 seems like just city. Is that right? If it is, those numbers seem okay. (especially with the a/c on)

kyoso23

For the record, I get around 19-21 with the AC on around town. Try again to make sure you started with a full tank. If you are still having that bad of mileage, you might look into cleaning your sensors and replacing the o2's.

over40driv

It seems like with the A.C. on last night, I had a pretty good hesitation taking off at stop lights. Runs good at 20 mph on up. The above noted mpg was with out air, reg. conservative driving, name brand prem. gas. Went with Autolite platinums, wish I had went with Denso platinums. But I got good mileage with the Autolites when they were fresh installed. When I put in fuel injector cleaner my hesitation goes away.

over40driv

Also can you have a bad O2 sensor, causing bad gas mileage, and not have a CEL?

sc-driver

iTrader: (7)

The only way I see that happening is if your ecu is bad.

Check out this thread:
https://www.clublexus.com/forums/per...mely-rich.html

over40driv

You know a couple of years ago I had been out driving, came in and let it set for a while, my dad was in town. I fired it up and we were standing outside the car at the rear and there was this thick white smoke. I thought it was water in the mufflers. It hasnt done it again for 2 yrs. Ill keep a close eye on it. Dosent run better when cold, but Im sure a new ECU would be nice, wonder what Lex. dealer wants for one?

sc-driver

iTrader: (7)

your best bet would be to get a used one in the classifieds for around $100. The Lexus dealership is going to want at least $1000 for an ecu.

If you think its the ecu, try getting the capacitors replaced. That is what usually goes bad in them. I'm doing that this week.

horent135

iTrader: (10)

or u can wait until the bill is pass about cash for clunkers and get ur SC400 worth more money for a newer lexus!!

Hil

iTrader: (61)

Since I got rear ended I've been getting 10mpg city. I need to fix my car already

sc-driver

iTrader: (7)

why? is it cuz of a messed up alignment?

over40driv

My car def. runs just as good when warm, still havent put enough miles on to recheck the mileage. I had made a note in my receipt box on 5-13-06 22.8 mpg. I also cleaned and installed a new ground cable shortly after I saw the white smoke 2 yrs. ago.. Currently when you first start it, by looking you cant tell if its running as far as any kind of smoking.

sc-driver

iTrader: (7)

Usually the smoking is when its really cold outside and the car is at ambient temperature internally.
If its not doing any of the symptoms described in the other thread then it might not be the ecu.

Have you checked your air filter and tire pressure. I know for a fact low tire pressure will make your mileage a lot worse.

over40driv

Always keep the tires at 32-34, air filter only has 5000 miles and never driven on dirt.