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Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 21717
Experience:  BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years
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2005 hilux 2.7l 3RZ-FE, excess fuel consumption

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Hi, I've got a 2005 2.7 petrol hilux ute. the fuel economy is terrible on it, getting as bad as 15.6litres/100 kms. Run it on several tanks of different fuel, (E10, straight unleaded, premium unleaded) all to no avail.
I've taken it to the mechanic to get them to check air flow meter, fuel pressure, i've put new leads, plugs and fuel filter on it too. It used to do around 11litres/100km and has gotten progressively worse. I'm still to take it to a toyota service centre and get them to put on their diagnostic testers. are local mechanic's diagnostic testers as good as Toyotas ? Can you get a glitch in the on board computers that control the fuel system and therefore reprogram the IDS computers? any help with suggestions into the excess fuel use would be awesome....


This could be a number of things:

Incorrect fuelling due to a faulty water temp sensor. If this is the problem then the ECU will be leaving the car constantly ' on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner ( not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead- if this doesn't help consider replacing the sensor as they're not expensive

Check for exhaust leaks before the O2 sensor as if this has been experiencing an exhaust leak then it will have been running very rich as the sensor will see the extra air pulled in as fresh / lean fuelling and be adding fuel to compensate.

this can lead to catalyst failure as the extra fuel can re-light inside and melt the catalyst

The best way to find an exhaust leak is to run the engine from cold and feel around the exhaust joints with your bare hands - you'll have about 30 seconds before it all gets too hot and you should feel any escaping gas blowing over your fingers

Air leak at the mass airflow meter -
Any air dragged after the meter isn't 'seen' by the ECU and so not compensated for, causing rough running.
Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.
The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.
Binding brakes:
Check that all the wheels can be turned freely by hand, and free off any sticking calipers
Incorrect wheel alignment:
Check all the tyres for signs of uneven wear if it has any then get it checked out at a place that does 4 wheel alignment not just front tracking and ensure tyres are pumped up to their recommended maximum
Injectors are clean and not dribbling - add a bottle of injector cleaner to the tank

Use good quality fuel - from my own findings its worth paying the extra for BP or shell as typically you'll get another 10% fuel saving which outweighs the cost over supermarket fuel.

And the biggest thing is driving style, by not labouring the engine ( too high a gear up hills etc) and not accelerating hard away from the lights etc you can usually improve things by another 25-30% or so.
Matt and other Toyota Specialists are ready to help you
Customer: replied 5 years ago.
Thanks Matt.
I forgot to mention I had the mechanic replace the coolant temp sensor, and the O2 sensor, used injector cleaner.
I can appreciate there are a lot of variables for this type of problem, so thanks for your reply

It sounds super rich when you go say, up a slight hill in 3rd gear when driving around the back streets, the motor to me sounds like too XXXXX XXXXXke way more fuel's being supplied to the mix.
On start up and idle, the engine runs fine the doesn't run rough as such. The driving style of late is much more conservative than before I noticed a problem with it. The 2.7L hiluxes hammer along, and I before i noticed the fuel problem I was getting plus 400kms out of a tank, driving like a man possessed.
Now I'm driving like a pensioner and i get 300-400kms at the very best.
I haven't had any substantial weight in the tray either.

Will get an alignment and check the vacuum leaks and the exhaust leaks before the cat.
Maybe there is a crack in the exhaust system that's avoided detection till now.

Keep you posted I guess.
Let me know what you find and I'll try to help further