Increased fuel consumption - 2002 TD Prado

No - tyres were changed at 70000km...

This increased consumption has been consistent over the last 20000km which has taken 12-18mths to travel - summer/winter no difference...

same size tyres, 265/70R16. I have also heard the Shell diesel getting better economy story, and yes, thats what I use!
Thanks for the reply.

Thanks for your reply. All good points, but the accessories were fitted almost from new and i was still getting the good consumption, then it suddenly decreased. I was thinking about the injection timing myself, though dealer says it never needs to be touched...

Just re-read your response - does a snorkel restrict airflow? Have never heard that before, only that they help your engine breathe easier through the cleaner air from higher point of intake, plus ram effect (though I've also read that this is negligible at speeds below 200km/h!)

Rich

Timing belt stretches with age and timing progressively becomes more retarded.

With the snorkel, it has more bends and thus restricts flow, ram effect is negligable.

John D

Thanks for the extra clarification. Still feel the snorkel not the culprit as I had it fitted at about 30000kms, fuel consumption didn't go downhill till 60000kms. Timing belt not scheduled for replacement till 150000kms from memory, this car has had a very cruisy life, lots of highway running, a little bit of city stuff and the rest cruising around the suburbs and up the mountains so hopefully the original belt isn't stuffed yet..

rich

Take your snorkel air ram off (only one clamp) and check to make sure the wallies who fitted it didn't put the restricter washer in (for petrol models to cut induction noise). I have the same motor as you and when they fitted mine they put it in, it HALVED my air intake size!! Takes 1 minute and a screwdriver to remove.

Run your tyres at 42psi, you'll get HEAPS go from standing starts and much better cornering, less tyre wear and save a fair whack in fuel.

I've actually been experimenting with mine at 48psi to try and combat the excessive fuel I use in the school run each day (dropping my son and picking him up, it's about a 15k round trip of constant stop start cornering below 70kph driving. I havn't noticed much of an increase from 42psi fuel wise, but the ride is a little too firm. At 32psi I feel like I'm towing a trailer I loose that much power, so it would have to effect fuel consumption alot IMHO.

The type of driving you do will make a huge difference too. I get anywhere up to 17l per 100kms on those constant short round town trips, on the open road with a FULL load on the roof rack and in the car, crusing at 80-90kph I can get as low as 10.5L per 100k even with the air con on about 25% of the time.

The old rule of thumb I was told was a saving of 2% in fuel economy for every 2 psi over 32psi. Less rolling resisitance, but it maxes out at about 40/45 psi.

Hi and thanks.. No warning lights coming on, no temp increase. Everything running like a train so feel even the injectors are fine, though I could be wrong - I frequently am! LAst major service (70000kms) was at an ARB workshop who I took it to for this very reason, they say everything is tip-top ship-shape so i'm really stumped.. I haven't been back to Toyota as its out of warranty and I'm predicting a big bunfight plus the person who works on your car likely to not be as 4wd inclined as say ARB? I've now moved quite far away from the ARB workshop..so either back to Toyo or find another 4wd/diesel place with some knowledge. Getting very frustrated as it costs me at least $20 per week in excess fuel..

Might I add I'm probably the lightest foot going around, I always drive for economy, even more so these days! If I drive it with a heavier foot, it drinks juice like a v8...

Sounds very much like a faulty airflow sensor or the Engine Control Unit is at fault somewhere. Still could be the injectors (doesn't take much to screw up the atomization) . Just a small possibility when it was serviced about 20,000klm ago was the gearbox transfer & diff oils changed ? To heavy grade of oil can lead to increased driving resistance therefore increased fuel consumption.
I would have the E.C.U reset back to default settings & go from there. All so were the injectors removed & tested? because it is impossible to properly check atomisation while they are still in the eng. ARB are good but you are better off going to a diesel specialist when it comes to the fuel system (eg united diesels or even a Cummins workshop) Hope this can be of help......666toy

1kz-te doesn't have an airflow meter, only a air temp sensor which wouldn't make much difference.

You wouldn't be able to tell if it was running hotter as the toyota temp guage only has three settings, cold, normal and hot. Once you get to about 65-70c it will slowly rise to half way (or there abouts), then it will not move again until you hit about 110c. But in saying that I would think that you would get better atomisation of the fuel at a higher temp anyway, so that shouldn't matter.

Richie
You say you have shifted camp, does the new route have (a) more traffic lights (b) more hills (c) more roundabouts ?

eerfree

"I haven't been back to Toyota as its out of warranty "
Dont these have 100,000k's warranty?

eerfree - this new route is very recent (about a month), the fuel consumption increase is something that happened 20000kms ago and has been consistent ever since. The new route involves more freeway/highway driving but still getting nowhere near the economy of the first 60000kms of the prado's life, where driving in the suburbs/peak hour grind would still return 12l/100, now I barely get that on the highway.

Fisho64 - warranty was 100000km/3years - vehicle now 4.5 yrs old..

Cheers all

Thanks for reply - no roofrack (did have one for a short time - chewed fuel like nobody's business so i took it off). Doubt that Shell are using biodiesel - wish they were! Tyres wearing normally, no alignment issue that I can see.. Radiator/intercooler are clean (I really must get offroad more often) and again, I would expect the fuel from a high turnover Shell outlet would be rather clean..about to change the fuel filter so will look out for any change in consumption..

Thanks again

I don't get any difference in using 100% biodiesle to when I was using dino diesel so I doubt there is an issue there (same engine).

Please don't assume Shell are any cleaner than anyone else, one of the work cars got a bad dose from the Shell in the Blue Mountains, the name of the town escapes me, it was closed for a short time till they sorted out the tanks.

Bio Diesel will increase your fuel economy and reduce your power, well it did for me.

Biodiesel actually has a higher cetaine level that regualr diesel, however if you are running it in a colder environment that may explain your decrease in power/economy, perhaps a fuel heaer run from your radiator would do the trick. I've done over 20,000 k's this year on 100% Biodiesel and belive there to be more power, especially once your donk has heated up. But then again, it is pretty warm in Perth, even in winter it doesn't get cold cold.

I agree with the Shell comment though, I used to do a lot of work at servo's quoting and installing security systems, some of the tanks that come out of "branded" sites are disgracful, and often the private sites have put new poly tanks in before they have opened the site, so even though they may look old and daggy, they are probably selling a cleaner fuel! :-)
The moral is, you just can't tell by looking at a servo as to what the quality of the tanks are like underneath. It's a luck of the draw. If you see a servo in your local area getting new plastic tanks put in, go there - that's my advice.

Will check the airflow sensor idea on the yahoo group, though a bit reluctant to play with delicate items! Thanks

what i meant was dust on the air flow sensor can well you know bugger up what it senses, I think they clean it with compressed air.

Theres no airflow sensor on the 1KZ-TE.

Oh well, i did say i didn't have the diesel. The prado group site is still i think the best bet for an answer.

Yeah they are a funny thing, I'm not sure exactly how they work but the pump is driven mechanically (by the timing belt oddly enough!) but it has somthing called an "injection pump timing control valve". Bugger if I know how it works... I guess if that valve or the throttle position sensor or somthing else is not working correctly the timing could be out...

Try taking the battery terminals (both negatie and positive) off for an hour or so and re-connect, that will wipe the ECU memory (you have to remove the neg for that to happen though) and you may find that when it restarts it will adjust to you current fuel, dirving etc etc better. I did that when I changed to BD and it made a noticble difference.

I have 53000 k`s on my 2003 Td prado, and still have Grandtreks on with a fair bit of wear in them yet.

They are rotated every 5000 k`s with very little uneven wear.

The fuel has Pro-ma diesel additive added, using between 10 to 11 L/100 K`s on highway driving and 16-17 L/100 towing a van.

Djrziggy - did u mean 150-200kms less per tank?

I did have uneven wear on one front Grandtrek, but the Cooper At/r's currently on seem to be wearing evenly. Just about to give them their first rotation (approx 10000kms).

Rich