Another Poor Fuel Economy Thread

[CMF_playasyougo]

Hi,

Not long after finally getting my Micra running after a faulty fuel pump, i've started to get really bad fuel consumption.

I put in £14 or about 11 litres and managed to get around 70 miles in a 1998 1.0 Micra! My previous Honda Civic with 1.8 Integra Type R engine used to get much better than this!

So far i've done the following:

Checked tyre pressures
Replaced throttle body and 02 sensors with 4 different ones
Checked ignition timing
Checked exhaust gases with garage equipment and all readings and values are as stated in the Autodata software
Hydrocarbons are really low
Checked for sticking brakes
Checked for leaks
No fault codes on dash or when Autodata diagnostic is plugged in

Anyone have any ideas?

I noticed mention of there being two different coolant temp sensors. Could it be possible the one going to the ECU is faulty? Surely that would still show that if it was and causing over fueling then the exhaust gas analyzer would have picked this up?

Cheers

David

 

[CMF_playasyougo]

Should have mentioned, i tried the 2 pin idea on the diagnostic plug and when i bridged the two lower left pins nothing happened.

Pretty sure i couldnt have got it wrong so no idea why i never managed to get any flashing lights on the dash.

 

[CMF_frank2]

thats over 30 to the gallon eh david, about right for town driving, tho you should be able to get nearer to 50mpg at a steady 60ish

 

[CMF_Greo]

Mayb try a differnt fuel type. Any with a Ethanol normally kills economy. Shed any excess weight from the car too.

A huge influence on the cars fuel economy is how much lead is contained in your foot. ( a driving style change could probably find a few extra MPG)

 

[CMF_Bishop]

Checked your engine thermostat?, where does your temp gauge generally sit?, I know the thermostat on mine is on the way out, car runs too cold all the time (they lag open with age), and modern cars run their best fuel economy when fully up to temp.

 

[CMF_playasyougo]

The car gets up to temperature fine and the gauge reads half way from bottom to top. It always has.

I've tried driving as slow as possible but the issue is still there.

Here is a photo of my fuel gauge. I put in £30 or 23 litres where it sat on the line marked with a Red circle. The display shows i've done 87 miles using that much fuel. That's no way right in my opinion.

 

[CMF_sikK11]

You tyre pressure????? Make sure it's between 32-36psi all round.

 

[CMF_adz14]

You can't accurately know how much fuel you are using unless you used full tanks. Fill it right up, reset your trip meter. Next time, fill up again and then calculate your fuel usage. Unless you do that, you are just guessing.

 

[CMF_sikK11]

And you have not posted about resilderimg your throttle body. From previous threads that can cause crap economy

 

[CMF_Greo]

there is an iphone app that can help track ur fuel economy its called 'Roadtrip' the lite version is free.

i have found it usefull in tracking my consumption

 

[CMF_playasyougo]

Tyre pressures have been checked and all are at 33psi.

I understand it would make sense to go off a full tank but getting 70 miles to £14 is bad and putting in £30 and it now almost sitting on the Red after 99 miles (todays driving)looks very poor to me. At the rate it's been dropping i will only have another 20 or so miles to go before the low fuel light is on so that's roughly 120 miles for £30. Poor no matter how you look at it for a 1.0 litre engine.

As mentioned above, i was getting more than that to about £20 with a 1.8 200hp engine.

One of the multiple throttle bodies i've fitted has had the AFM joints re-soldered. Still the same.

Sorry, i dont have an iPhone.

Cheers for the posts guys.

David

 

[CMF_Mike R]

I would of expected just under 200 miles , each little segment on the fuel guage gives me just under 50 miles on my car . even when I had a faulty MAF it still did good mpg but had no power , now it has power and slightly lower mpg with the new TB . Tyres are at 33psi , all excess weight is gone .
Check the brakes they can bind when running for a while , I had a front offside one bind , garage admitted for some reason its always the offside front ????? , gets really hot after a few miles despite being ok when cold.

would also do a plug check , perhaps the engine is ok but the fuel is going somewhere else , sounds daft but check oil level etc is not changing

 

[CMF_sikK11]

Could be a small pin hole creating a list spray when under load and your fuel pressure picks up? But I am sure I am over thinking it.

 

[CMF_Bishop]

Mike R WROTE:
even when I had a faulty MAF it still did good mpg but had no power , now it has power and slightly lower mpg with the new TB

Funny you say that, I had a throttle body fault, which in the end stopped my car dead, with a now resoldered fix, it's gets a little less mileage then before it all went wrong.

Wild guess, something the solder fault may make the micras run lean...

Back to original guys problem, looked at the FPR?, or gotten a fuel pressure test?, faulty fuel pressure regulator will make many cars run rich, actually does the car smell rich in the exhaust, if it's running rich enough that you think mileage is a fair way off, you can usually smell it.

 

[CMF_Mike R]

mine was a Bosch MAF which finally stopped the car one cold morning .
but yes the car would smell rich sometimes , not pull or rev when cold , and had a lack of power when hot

 

[CMF_super_slav]

WOW, thats way worse economy than my Pulsars SR20DE engine, I get around 600km highway milaege and last time i drove i got 530km mixed highway and city. Check your oxygen sensor.

 

[CMF_playasyougo]

Not sure if you read the above

 

[CMF_hunterz]

Hi did you have any progress with your fuel economy.

 

[CMF_Mike R]

interestingly I have just had my front drive shafts changed and the gearbox refilled with fresh oil ....cv boots had ripped .

just before that I changed my back tyres round and now have two Dunlops that are getting low on tread as opposed to two pick n mix budget tyres

as a result I have hit 200 miles before even getting to the 180 mile mark on the fuel guage ?????

only other thing is the weather has got a lot warmer ..

 

[CMF_playasyougo]

hunterz WROTE:

"Hi did you have any progress with your fuel economy.

Hi,

I managed to get slightly better figures when i changed the coolant temp sensor for the ECU.

Still reckon there is something wrong though as the car has a strong smell of petrol when its being used.

Still got better mpg with my Honda but i only have this car as a beater to use until August when the car i'm building will be on the road.

David

 

[CMF_mycra]

personally i think there are heaps cars out there that are more fuel efficient... it's the way it is with engines, cars... my honda's had 3 engine transplants, my current b16 burns more than my previous K20 believe or not. the 1.4L Holden burns same as my Honda dont matter what i try and the missus 1.3 Suzuki gets 650kms out of 33L on 91oct... With K11 been an euro built car best fuel to run is 95 octane(10%eth, 91,98) all burn crap.

funny thing is when you modify the K11(cams, flywheel) you get better economy lol

 

[CMF_Greo]

mycra WROTE:

"personally i think there are heaps cars out there that are more fuel efficient... it's the way it is with engines, cars...

funny thing is when you modify the K11(cams, flywheel) you get better economy lol

I have found this with my micra too with the CAI and more bouts of 'spirited' driving (the induction noise encourages you) I'm getting marginally better economy then with standard box.

A lot can is the body of the cars too. A small engine only has good economy if its in a small/light car.
Seen some euro diesels that have terrible economy due to the need to be on limiter just to maintain the speed limit. (I remember seeing a Top Gear episode where Jeremy had to fill up his 'economic' small car due to its under powered engine)

 

[CMF_mycra]

if you cruise on a steady 75km/h on the freeway, a full tank 95oct gets you 720kms. if 100km/h you get 520-550(same as my city driving). if you go 98oct @ 100 you get 420kms. funny hey..

also with mods it's not exactly "fuel efficient' but it take the motor less effort and time to reach desired speed.

 

[CMF_frank2]

mycra WROTE:

funny thing is when you modify the K11(cams, flywheel) you get better economy lol

i agree, (and compression too) mine,s surprisingly good on fuel, i used to get 100 miles on a tenner with the lpg one so expected about 60 miles with this petrol one, but its averaging 75 miles
which works out at 10 miles per litre (16 km / L)