Extremely bad fuel economy - 2TZ-FE

My 1992 Previa, 2TZ-FE 2WD, auto trans, is (and has done since I've owned it) getting about 11mpg (22 L /100km). Is believe this is excessive, and would expect more like 20mpg (12 L/100km). Am I dreaming expecting this? This motor runs very well, has fresh plugs/leads filter etc? What could be causing this poor effeciency?

Greg

Reply to
Greg
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Thank you Mark for the reply. Tires are near new, and fully inflated. When I say the motor runs well, it 'seems' to run well. Starts quickly first try, runs smoothly. No ECU codes last time I checked. What maintenance items can affect economy? I have no problems repairing / replacing parts, It's the diagnosis I have problems with.

Thanks Greg.

Reply to
Greg

Mark,

1) No gold bars - in fact most of the time no load except a few young children. 2) Yes, I am a little bit of a lead foot, but my wife gets about the same MPG, and she drives very conservatively. 3) I'd like to see a Cadillac do that........................ down a mine shaft ;-)

Greg

Reply to
Greg

My wife got 14-16 MPG in our normally aspirated '93 Previa around town, I usually got 16-18. I'm a little better at backing off the throttle to allow the transmission to up-shift and to anticipate stops.

Check the condition of the ATF to make sure it is not burnt and the transmission is slipping. As the transmission is going through the gears, make sure you count all 4 gears and torque converter lockup (which is difficult to detect). Inflate the tires to about 32 to 35 PSI for better fuel economy. Check the brakes to make sure they are not dragging.

Reply to
Ray O

Thanks Ray. I replaced the ATF a few months ago to correct (unsusfully) a shifting problem. It turned out to be a broken wire from the ECU to the TPS. A continuity test found the problem (after suggestion from someone in this group) end ECU code confirmed it. Trans now operates well, 4 gears & torque converter lockup. Tires inflated to 34 PSI, new brakes & wheel bearings, no dragging. I'm starting to run out of ideas. Would a clogged PCV vale have a detrimental effect like this?

Thanks again, Greg

Reply to
Greg

A clogged PCV valve won't cause that kind of problem.

Get a bottle of Techron fuel injector cleaner at a Chevron station or auto parts store and follow the directions. It's possible you have clogged or leaking injectors, although they usually cause drivability problems.

Also check ignition timing and advance, make sure the air filter isn't clogged.

Do you have anything mounted on the roof, i.e. aftermarket roof rack?

Reply to
Ray O

I'll try some injector cleaner, not sure if Techtron is available here (New Zealand). What should the ignition be set at? I have no manual. It was imported used from Japan, if that makes any difference. Air filter is new.

Thanks, Greg.

Reply to
Greg

For a U.S. Spec 1993 Previa: With the engine at operating temperature, short terminals Te and E1 with a paper clip or stiff wire. Ignition should be 5 degrees before TDC at idle; remove the short and ignition should advance to 12 degrees BTDC. If you're looking for a power source for your timing light since you're so far away from the battery, hook the positive lead on the timing light to terminal 30 on the starter.

If Techron is not available in NZ, use some other name brand fuel injector cleaner.

Good luck!

Reply to
Ray O

Thanks a lot, I'll give it a shot and post results !!

Greg.

Reply to
Greg

You're welcome!

I checked the factory repair manual. The only other things listed for poor fuel economy other than what I have listed are low compression, fuel cut, EGR, and MFI.

For cylinder compression, they should be within 10% of each other and at least 128 PSI.

To check fuel cut, with the engine warm, increase engine speed to over 2400 RPM, release the throttle, and check to see if the injectors stop opening until RPM drops to 1800 RPM. You can put a stethoscope on the injectors or put your fingers on them to feel them stop pulsing.

EGR should be opening and closing, not always on.

If it is an MFI problem, then it's time for a trip to the dealer.

Reply to
Ray O

Ray, I can check the compression and fuel cut. How do check EGR valve (more to the point - where is the thing?) What is MFI?

Thanks for answering my stupid questions.

Greg

Reply to
Greg

The neighbor's Cadillac can get that phenomenally good fuel mileage easily - all it takes is the owner of the Caddy siphoning gas out of your car late every night, and pouring it in his tank.

Try installing a locking gas cap on your car, and see if your numbers suddenly improve - and the neighbor kid suddenly has to start walking everywhere rather than drive his pickup.

Don't count on a gas door lock or inside door release for 'protection'. Those can be jimmied, sometimes very easily.

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Reply to
Bruce L. Bergman

Thanks for the advise Bruce, but it's locked, alarmed, and in a locked garage. I have been getting this milage since I've owned the car. Greg.

Reply to
Greg

The Exhaust Gas Recirculation (EGR) valve will be located on the exhaust side of the cylinder head and have a vacuum hose and hose leading to the throttle body. If you remove it, you should be able to see the valve opening and closing when you look inside where it mounts to the head. Applying vacuum to the port should operate the valve.

One other thing that you might also check while you're at it is manifold vacuum. Make sure you don't have a vacuum leak.

MFI is multi-port-fuel-injection and is composed of the computer, sensors, actuators, and controls.

Reply to
Ray O

Did you check alignement, O2 sensor and other sensors, EGR, etc? About a gas leak. Could be the top of the tank and you wouldn't see gas on the ground. Check for smell. (Don't ask me how I know this). Gas pump?

Reply to
Bassplayer12

I think Bruce has it. I can?t think of anything logical short of fuel leaking out on the ground to call for this kind of mileage. Toyotas are just too good for high mpg (or kpg) for anything else.

Reply to
rob

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