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Discussion Starter · #1 ·
Hi guys,

I have a 3rz-fe hilux. As far as I know our engines have no oxygen/lambda sensor, EGR valves cant seem to find the MAF sensor only what appears to be a air temp sensor.

Anyway, a while back about 8k ago she started getting heavy on juice from 15l/100km to around 19l/100km for no apparent reason..

Checked many things, tyres, brakes, major service etc. Getting to the stage where I would like to take it and set it alight. I didnt ride it for a week and now its a real dog show, getting around 20l/100km and I used fresh fuel. It sort of feels like something is holding it back, underpowered too. The engine is bog standard, only mods are 31" tyres and a canopy. Friends of mine are getting around 13-14l/100km.

I believe it has a vacum sensor but I dont see how this can get clogged or break as every Toyota dealer I speak to has never replaced one????

I would be grateful to anyone who can give me some adivce. :(
 

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You may want to try replacing your fuel filter, it may have gotten clogged and is not allowing the proper fuel flow therefore making the engine work harder and using more fuel.
 

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Hilux_3Rz said:
Fuel filter been replaced.. Do you think a dyno might be able to determine what the problem could be?
I don't think so.
 

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Hilux_3Rz said:
I have a 3rz-fe hilux. As far as I know our engines have no oxygen/lambda sensor, EGR valves cant seem to find the MAF sensor only what appears to be a air temp sensor.

I would be grateful to anyone who can give me some adivce. :(
Try to find a service manual for your truck.

Look at the ignition system, fuel system, and air metering system.

I can get you the Tacoma equivalent specs for whatever you need.
 

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Discussion Starter · #6 ·
I have got the service manual and all seems okay. There is no MAF sensor which i find is odd. What sensors etc are require for a EFI vehicle. Our 3rz-fe's have almost no emissions equipement and extremely simple for africa travel.
 

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Discussion Starter · #7 ·
No error codes come up on the diagnostic test by the dealer. And the SFB's say its fine. But 20l/100km at 100km/h is not normal!!

What else could be effecting it other than the engine? Could drivetrain or CV's have anything to do with it. Lifted the truck and the wheels rotate easily so I am a lost as to what the problem could be.

She is definately feeling underpowered now after standing for two weeks even with fresh fuel. At low revs its pathetic, seen shopping trollys move quicker..

BTW, SA 3rz-fe's have no MAF, no lambda sensors/oxygen, no cam position sensors.
 

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I don't know what features the scan tools at your dealers have, but our Toyota scan tools have numerous tests that can be performed, including fuel consumption.

Beyond the engine, it could be drivetrain load or tire pressure, etc.

This is one of those problems that is hard to diagnose without having access to the vehicle.
 

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There are several types of basic EFI systems. Alpha N systems are based on RPM and throttle angle only. Alpha N systems are OK for race cars but little else as they impose no restrictions on engine air intake.
Speed density systems base fuel and timing by estimating the intake charge and engine load by manifold pressure, RPM, and throttle angle. Corrections are made for intake air and engine cooling. They may or may not have closed loop operation based on feed back from an O2 sensor in the exhaust. My guess it this is what you have but without the O2 based closed loop feedback.
The systems in common use in the US have a MAF sensor that estimates engine load by measuring the actual mass of air flowing into the engine. MAF based systems also estimate fuel and timing using Intake air temp, engine temp, throttle angle and engine speed. Sometimes but not always manifold vacuum or pressure is also used with MAF systems. Most if not all MAF systems use an O2 sensor for closed loop operation. MAF systems do have a restriction in the intake imposed by the MAF sensor itself. A variation of the MAF sensor in older systems used a vane to sense the intake air velocity and determined intake air that way but these have disappeared for the most part as the mechanics were problematic.
Some systems are starting to be developed that actually measure engine output with strain gauges mounted on the output shaft or within the drive train somewhere. I think these will prove to be superior to anything else as they directly measure engine load instead of estimating it while also eliminating restrictions in engine air intake and they won’t be subject to fouling from dirt etc. as MAF sensors are. The only reasons I can think of why this doesn’t predominate today is that the automotive industry as a whole to so damn slow to do anything, they have also been historically ignorant and or stupid and fearful when it comes to anything electrical that they don’t already understand. As a group they are slow learners that adopt new technology only when forced to do so either by government mandate (also sometimes stupid things) or by market pressures when on the rare occasion one manufacturer has balls enough to try something new on their own and it becomes a hit in the market place and the rest of the pack piles on and plays copy cat.
 

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did the op ever figure this one out? my 99 prerunner w/ 3rz-fe is having horrible fuel consumption issues also. im getting around 15mpg to 16 us gallons. im looking at replacing the fuel filter and the VSV and maybe also the TPS. and possibly the pre cat o2 sensor. which one should i do first?
i also have horrible power and cant seem to maintain freeway speeds vary well and my automatic tranny is always shifting into passing gear to get back up to speed. maybe its my torque converter not locking up when i cruise? maybe i need to do a compression test also?

by the way ive been a tacoma world member for a while now and lurked ttora for a while but cant seem to get any serious help over there on this subject so i figured id you guys a try
 

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Stout, have you checked the usuals...air filter, and sparkplugs? How many miles on your engine? A bad O2 sensor will kill your fuel mileage, and may or may not throw a check engine light.
 

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Yes iv replaced the spark plugs and wires and cleaned the k&n filter. I don't have a propane torch to test the O2 sensor. I will look into one though so that I can


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3rz engine Fuel Consumption Problem

My car is a Toyota Prado model 2000 with a 3rz 2.7(petrol) engine
It's consumption rate is 4km per litre but I feel this consumption is too high and can't handle any more.
 

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3rz engine Fuel Consumption Problem

My car is a Toyota Prado model 2000 with a 3rz 2.7(petrol) engine
It's consumption rate is 4km per litre but I feel this consumption is too high and can't handle any more.
I know it's been 5 years but did you solve issure with your 2.7 Prado? I have a 95 series and it's getting about that as well. I don't know what else to do.
 

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New plugs/wires, change fuel filter, cleaning/testing the MAF sensor, testing the O2 sensor and cleaning the intake are all recommended courses of action for loss of fuel consumption. The ECU reverts to default fuel maps when it doesn't get proper sensor feedback. A good OBDII scanner to read live data will help point to problem areas.
 

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Thanks Showstop... Question: Isn't the 95 series Prado (1998) OBD I?
I'm not very schooled on Prado trucks, but assuming its a 2.7L engine, it would be OBDII. The 3.0L and 22RE were the last engines in the OBDI range. 3.4L and 2.7L are all OBDII.
 

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I'm not very schooled on Prado trucks, but assuming its a 2.7L engine, it would be OBDII. The 3.0L and 22RE were the last engines in the OBDI range. 3.4L and 2.7L are all OBDII.
Yes 2.7
I always wondered about it, because there is no diagnostic port inside. The only port i see is the one in the engine bay.
 
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