RobD

Not "my fuel injection system", per se. I mean the 3.4 has a better overall intake and fuel system than the 3.0 does.

Tofer

94 4runner
5sp
about a 4" sas
35x12.5 bfg mts
5.29

14city/wheeling
17 hwy

skunkwhat

ok ok, i get it now, you were comparing the 3.0 to 3.4 and the 3.0 having to work harder.

Originally i thought that you were saying the 3.4 didnt have to work as hard at a higher rpm, as opposed to a lower rpm, like if it was being lugged.

UKrunner

Confirmed the TC is locking up but still getting 11mpg. I wonder if having my cone filter attached right at the maf is causing issues?

RobD

Doubt it. That's where I have my filter.

UKrunner

You guys running premium or regular?

Just calculated and got 11.76mpg for todays 106 mile trip. 98 miles were highway at 70 - 77mph. Something is very wrong. There is no black smoke or smell of raw fuel in the exhaust except for when cold. I still do not have the O2 sensor connected but would be shocked if that brought me up 5mpg. I do have a smell of fuel vapor but cannot find anything wet anywhere.

Does the ecu control fuel pressure by pwm'ing the pump? Mine is hard wired currently, to be on all the time the ignition is on and not controlled by the ecu. Also, I have no emissions equipment at all. The 3.0 canister is on and the tank hard line is connected to the "Tank" input and the purge line is plugged but that is it.

I do not have the characteristic surging related to a maf issue and all wires have continuity between maf and ecu.

RobD

I'm just running regular. I noticed negligible difference running premium.

I'm not using any of the EVAP or charcoal canister, either. We don't have your draconian emissions checks, so I never really got around to installing any of it.

Wheelingnoob

I do not have a 5VZ yet but have lots of years with Toyota's. Not having the O2 sensor hooked up will give you very bad millage. The ECU will be in a limp mode and dump in extra fuel to be on the safe side.

In my Supra with the 1jz I swapped in changing the O2 sensor netted me an average of 7MPG improvement.

Also you say you have the hard line from the gas tank hooked to the 3.0L charcoal canister and the purge plugged? That can needs to vent some how you can plug off the system you will get a build up of pressure in the tank and I have no idea what effect that will have on millage but I bet its not good.

Try the O2 sensor first and then play with that Charcoal canister. On my Supra I never ran a canister with the 1jz or the 2jz and just had it hooked to a hose to the filter to suck up the fumes.

Good Luck!

skunkwhat

the fuel pressure is regulated by the regulator, the pump just pumps it, and the regulator returns what it does not need.

UKrunner

Thanks for the suggestions and comments guys. I just took a 1000 mile fishing trip this weekend and averaged 14.3mpg at anywhere from 55 - 77mph.

I'll definitely get the O2 sensor fitted. I'm surprised it will net that big of a gain. I also had no idea I was in limp mode. Seemed to run smooth and pull just fine.

Everytim e we filled up, for about a 1/4 of a tank we could smell fumes with the windows open. Guess I'll run the purge line to the intake and suck out the fumes.

mrbags

85 runner.
5.13 one ton axles.
40 inch tires
12 - 14 mpg

UKrunner

Ok, so after waiting too long I recently got an O2 sensor bung welded in. I also replaced the fuel pump bracket as a hard line had rusted through. As I was taking the tank out I found out where the original raw fuel smell was coming from - which I mentioned a couple of posts up. The small breather pipe connected to the filler neck had completely rusted off and was hanging there.

So, with O2 sensor, new pump bracket and lines, and new filler neck. I now have no smell, a pressurized tank, the emissions CEL is out and.......... 15.94mpg!!

Yeah for 3mpg improvement driving with a lead foot! The last 6 or so tanks I'd been getting anything from 11.9 - 12.5mpg.

Strange thing that I noticed. Previously the low fuel light would come on and I'd be able to squeeze in 13.5 gallons and have driven 150 - 160 miles. The gauge was very close to E. Today I put in 13.2 gallons but there was a 1/4 tank left according to the gauge and I'd driven 211 miles. I wander if dropping and moving the tank around dislodged the fuel level sender and it works better now?

UKrunner

Wife did a 240 mile round trip in it the other day and returned 17.36mpg. The range on a tank is now ~260 miles.

vital22re

iTrader: (2)

I'm getting 16-18 depending on speed and the wieght of my foot. I'm also supercharged. I will switch to 4.30's to help with the highway mileage. seams that around 2500 is the sweet spot for mileage.

hamish_18

bah that isn't fair. I don't get as good as I should because I have 5.29's and 35's. so for me 60 mph's is around 2800 rpms. I wish there were a way to put in a higher 5th gear...

UKrunner

I'm running 4.56's with 265/75/15 tires. 70mph is 2900 rpm.

hamish_18

ya speedo says like 68. but my gps says 60.

vital22re

iTrader: (2)

according to 2 different gps sources, 70mph @3000rpm on my speedo is 68. I'm 2mph slower than gps.

runnerMike

I've had the 3.4 in for 2 weeks with mixed driving, still getting 12-13 mpg. I have 35's and 4.88s. 2900rpm at 70 mph on the freeway. I,m a little bummed that it didn't improve more but the new found power makes it funner to drive.

Fernley1

Having my 3.4 swap done for about 3 months now, my gas mileage is @21 MPG on the hiway. The last big trip I took was over Donner Summit and my truck was loaded with camping stuff, still got 21 MPG.
91 Extra cab
5 speed
31 inch AT tires