The Conundrum that is the 1UZ - Fuel Economy and smooth running/flat spot?!

[nathanshnoz]

nathanshnoz could you check VF1/VF2 voltages when the engine is heated to operating temp and gradually revved through the rpm range you typically use?
2.25V would indicate either perfect engine condition , or some failure in fuel mixture monitoring. The thing making me believe there's some failure is that both voltages (which indicate fuel trims for bank 1/2) are ideally matched, though in old engines the difference between the banks must build up.

I'd advice that you at least emulate the sub o2 heaters so ecu won't flash sub o2 codes. For some reason fuel consumption is sensitive to sub o2 sensors

I will check voltages tomorrow mate and let you know. How do you emulate the sub O2 signals? Ill double check fault codes

Also I have a spare ECU, so I have tested with both and there does not seem to be a difference

[4th surf]

Might have your answer, doing another 2 at the moment with stock ECUs to get them engineered and regoed. Giz a yell at your leisure

[George]

How do you emulate the sub O2 signals?

I use electronic emulators. I'm sure ebay has a number of them. Any Toyota/Lexus ECU up to ~2003 is fooled quite easily, so even the cheapest ones would work nice. To run them successfully, you need to make sure the main sensors are ok, and additionally emulate sub-o2 sensors' heaters with resistors.

[nathanshnoz]

4th surf I sent you a PM mate.


George I have had a look on ebay and can't seem to find them

[George]

http://www.ebay.com/itm/DSP-Toyota-O...208552&vxp=mtr
http://www.ebay.com/itm/DSP-Universa...2072c9&vxp=mtr

[dumbass]

gee at those prices for simulators u might as well fit proper rear o2s
ive done shitloads of 1uzs and afew were the ones where which run rear o2s and never ever have hooked the rear o2s
and never have had complaints about fuel economy

can anyone confirm 100% that missing rear o2s is the issue

the reason rear o2s started being used is so the ecu can bring on the check engine light when the cats fail when there is too much difference
the before and after o2 readings

fk the 1uz off and fit a 6lt ls2 atleast u can turn the o2 sensors off hahahahaah

[George]

Mine add only $42 when installed along with immo bypass but I don't sell things at ebay hehe
Mate's LS430 (european market model) ran worse and had the warning light on when only downstream sensors' heaters failed (both within a week, surprisingly). My emulator worked for the car, though being cheap and simple. Post 2003 cars often require more sophisticated emulators, I think those on ebay are that.

[nathanshnoz]

I ran the engine check codes and only get code 21 at the moment which I believe is left primary O2 sensor. Can anyone confirm which side (physical) is the left side? (Passenger or drivers?) O2's are
Only a couple of months old so seems strange if one is not working. Unless the plugs are damaged.

[George]

sensors are located at both driver and passenger's sides
there's total 4 of them. Each bank has 2: upstream and downstream sensors, called primary and secondary respectively
bank 1 is located on driver's side on lhd vehicles

if the code appears immediately after reset (battery disconnect) then it's heater circuit that failed

[nathanshnoz]

ok I DO NOT HAVE SUB 02 sensors fitted.

i have never had them fitted. my understanding of sub O2 sensors is the same as dumbass above. perhaps they do make a huge difference and perhaps they do not. at this stage i am not willing to go out and spend lots of money on sensors unless someone can convince me this is going to be the problem. i think the problem may lie elsewhere. we are talking about 20L per hundred Km's type stuff here and that's not driving hard at all so i find it hard to believe not fitting sub O2's makes a difference of 5/6L per hundred kms.

[dumbass]

Get your main o2s working

Wire up the half moon diagnostic plug and get a scanner, live data is much easier to understand

My hilux which was 50 to 55 lt tank got 300 kms distance on a tank
So yours ain't that much worse
People should really come to terms they are not a good motor overall when fitted to a 4wd or similar

[dumbass]

I could drive mine hard or soft and it used the same fuel
Diff ratio plays a huge part on fuel economy of these motors
Plus I've also had a friend with hilux but he had a 1j and he lost heaps of
Economy when he changed his diff

Doing 2500 rpm at cruising speed uses less fuel than 1500 rpm at cruising speed