Excessive Fuel Consumption

[mudinuri]

Hi all.

Any help and advice would be welcome on the following problem.

My 1998 RAV-4 3 door manual 2.0 litre is only returning 20 mpg.

I genuinly drive carefully without flooring the throttle. I try to get her into top gear as soon as the engine revs are right.

What I have noticed is that sometimes the engine runs on when I take my foot off the throttle and I have noticed on the odd occassion a slight smell of petrol, but not all the time and not over powering.

There are no fuel leaks and I have a new Air Filter fitted.

It sometimes feels like the Choke is sticking on, like they used to do on older Carburettor engines, but I know this engine has Injectors.

Any ideas?

Cheers .

[Mr.Fixit-Norm]

Hi David,

I'm no expert but what sort of mileage has she done? I'm think worn injectors maybe. On older cars I've had running on has usually been caused by a badly carboned up head, the carbon is still glowing after the ignitions turned off and it keeps the engine running for a few seconds more - I had an old Ford Escort van that would run on for about 20 seconds after turning the ignition off ! When I took the head off it was clogged with carbon, took ages to clean up.

HTH

Norm

[crofter]

Has the air flow meter been cleaned ?

[LeeroyJones87]

Hi mudinuri,

Is this a 2 litre petrol or diesel?

If petrol, double check the fuel tank isnt leaking.

If diesel, check fuel filter for it being clogged and renew.

Toyotas do tend to run on after blipping the throttle, i dont know why but its just a thing some of them do.

Finally, is your journey stop start, 30mph ish driving or more lengthy journeys at 50mph +?

Hope this is of some help.

[mudinuri]

Hi all,

The RAV has covered only 107000 miles and uses no Oil or Water.

What is the Air Flow Meter, where do I find it and how do I clean it?

and as I said, she is definitley not leaking fuel. Most of my runs are short with the ocassional longer run.

Cheers all

[LeeroyJones87]

Hi again,

I'd advise against cleaning the air flow meter which is on the inlet pipe after the air box.

If you try blipping the throttle pedal at idle and in neutral, see if the engine hesitates. So it'll sound like you've double b lipped the throttle pedal but you only blipped it once.

If it does hesitate the car will need a new air flow meter as this will cause excessive fuel consumption.

Hope this helps

[jockstrap2011]

I disagree with the above.

My corsa had a poor working air flow thingy and i greased it up with that copper stuff to help it work smoother and it ran a dream

[LeeroyJones87]

Erm ok

[LeeroyJones87]

But seriously try what I posted mudinuri and see if it hesitates.

Toyotas are miles different from corsas

Hooe this helps

[jockstrap2011]

Not worlds apart, i have friends with toyotas and stuff

Why you always right?

[Awebb180]

an air flow meter is a hot wire that measures the air coming in, do not grease it up this will hinder the performance

Alex

[LeeroyJones87]

Cos I work on 'em

[LeeroyJones87]

Alex is right

[jockstrap2011]

But surely greasing the hose will make it flow faster cos its slippy and stuff

[LeeroyJones87]

Err no it doesn't work like that jockstrap2011

[crofter]

With you all the way so far Leeroy, but cleaning the MAF (carefully)or fine wire filiment has been discussed before on these pages and found to be beneficial. They do get dirty and affect readings and a "change it and see if it helps" is not the way we tend to go as if we can keep down costs that has to be better and we do like fixing things ourselves

Some of us are complete numpties (and admit it) and some of us where born with a spanner in their mitts.

Keep up the good work matie

Del

[LeeroyJones87]

Hi crofter,

I'll go with you on this one too. If you are very careful, yes cleaning the

air flow meter can be done but precision and patience is what I'd advise! Lol

If this doesn't work, there are some decent non genuine products that do work well, to keeps costs down.

Thanks for the advice Del, Leeroy

[mudinuri]

Hi all,

If it is the Air Flow Meter, how much do they cost and is it a job a numpty like me could carry out.

cheers

[crofter]

Changing a MAF is a doddle as it sits on the top on the air inlet pipe. There are cables running to it thro' a connector,pull this apart then take out the holding screws and lift it carefully up not catching the sides.

You will find you have a plastic part in your hand that has a fine wire running from the top part to the bottom part.

It's a bit like a big open ended spanner with a hair across the jaws. the fine wire may have what looks like soot on it

DON'T try and wipe this clean,spray it with something like carb cleaner in an aerosol and try not to soak the plastic part with it.

It may take more than one application but it soon dries

Let us all know if you do this and how you went on,it's all knowledge passed on

Del

[Bodgit-fixit-run]

I've sprayed mine with brake cleaner which works a treat. A gentle blow afterwards with an air line helps too. The break cleaner will take any oily residue out of the soot prior to blowing.

Just take your time

[gjnorthall]

Some very strange advice given! A dirty MAFF will tend to weaken the mixture. Use MAFF cleaner or electric contact cleaner to thoroughly flush the filament of the MAFF meter - don't touch or rub the filament. Fuel consumption depends on many factors - ensure that spark plugs, air filter and fuel filter have been replaced in the not too distant past. Use a single dose fuel injection cleaner.

[bobby boy]

A compression test ,if you have the spark plugs out could be worthwhile .Confirms pistons and valves o.k.