ls400love

iTrader: (3)

Sean, our cars were designed with y-pipes because of the small displacement of the motor. As you already know our motor is only a 4.0L which is typically small for a v8. There are many 6 cylinder motors that are 4.0L's or near that number. The techs at Toyota knew this and chose a y pipe instead of an x for this reason. If you head over to the ls400 forum you will see this discussed many times(and tested) by forum member Jbrady. The ls400love has essentially the same exhaust setup as our gs4's. Search "Jbrady" under users in advanced search and you will find it. Members have dyno'd their cars with x-pipes and actually lost power.

Regards,
Milo

LoveThatV8

iTrader: (1)

I have a 06 GS430 and when I fill up tank to the max, dashboard tells me 250 miles to empty. Once tank hits about half, its sayin' i used up 125 miles already. So yours seem to be about average, considering the fact we have a V8 and a small gas tank.

dsgs400

My GS400 would get 100 miles every 1/4 of a tank. On average i was getting 19mpg. 400 miles total a tank. It's very much possible. The 2GS has an average mpg of 20mpg. But all of a sudden overnight my gas mileage dropped to 9mpg... i get 100miles on half a tank. And i'm sad.

Nilla

I feel your pain. I got a 99 gs4 about 115k. Tip top maintenance but i fluctuate like that. Sometimes I’ll get 180-200 to half tank. Today, This tank I’m at 120 @half tank. Always 93 Oct. I’m in va and now that winter is here it does idle more to warm up but still excessive gas being dumped even in fall. Good friend at Toyota does all my work and my fuel trims are running almost double what they should be. No cel, codes or anything. Even did a new fuel (denso)pump,filter etc. Not really a way to
pressure test the injectors on this old style thing. Unless you have some customer adaptors and what not. That’s my next move. I would guess your fuel trims are like mine?? Take to Toyota and have them
scan the cpu with their to see your stats?

DMPesso

have you changed your oxygen sensors and MAF sensor? Most of the time they are bad and will cause issues like you describe without actually throwing a CEL.

you people are lucky getting good gas mileage. I get 200 miles to a full tank with all this stop and go and traffic in NYC.

Nilla

I haven’t replaced those. The techstream scanner show all my numbers are pretty darn good except for that fuel trim. I might try the oxygen sensors if my buddy thinks it could help.

Dang 200 - tank is terrible. my mileage always gets worse in winter around 250-270. Summer time around city 300-325 I’m happy.

DMPesso

well o2 sensors are expensive if your replacing all 4, even Denso from rock auto. I’d start with a new OEM MAF or at least clean the one you have. It made a big difference cleaning and changing the MAF. If you don’t have any codes it makes no sense to change the oxygen sensors until you have to.

Nilla

No codes at all. New maf is $200. The o/s are about the same for all four from Rockauto. I need to clean the injectors but need to find a shop with the right connection for my fuel line. My boys Toyota shop doesn’t have them for this old car. He thinks I’d be wasting money on the maf and sensors

DMPesso

A lot of mechanics say a MAF is a waste of money but look inside and compare how shiny the platinum wire inside a new one is vs your old one. My foot isn’t lying when I felt the noticeable difference in acceleration after replacing my MAF. New oxygen sensors will only help gas mileage and overall make your car drive better since it’s 20 years old 100k miles.