Reasons for a loss of fuel efficiency

kupus

can anybody give any reasons for a loss of fuel efficiency?

there is a slight loss.
Tyres are fine, same driving, same route. nothing has changed. No sensors showing. The only thing is the battery has been changed as it had been going a bit wonky. Serviced regularly.

so barr dirty petrol or water moisture getting into the tank or a dirty filter any other ideas I can look into.

Renegade Mechanic

kupus wrote: »

can anybody give any reasons for a loss of fuel efficiency?

there is a slight loss.
Tyres are fine, same driving, same route. nothing has changed. No sensors showing. The only thing is the battery has been changed as it had been going a bit wonky. Serviced regularly.

so barr dirty petrol or water moisture getting into the tank or a dirty filter any other ideas I can look into.

Tyres may be fine but were they changed recently? Less efficient ones will affect consumption.

Hit any potholes to throw out the wheel alignment, thats a regular suspect that doesnt show till the wheels wear noticeably.

Drops in temperature mean a rise in fuel consumption (November to April generally)

A brake component may be starting to stick.

And how comprehensive was the last service? I'd recommend checking the air filter, youd be surprised what you might find!

kupus

Renegade Mechanic wrote: »

Tyres may be fine but were they changed recently? Less efficient ones will affect consumption.

Hit any potholes to throw out the wheel alignment, thats a regular suspect that doesnt show till the wheels wear noticeably.

Drops in temperature mean a rise in fuel consumption (November to April generally)

A brake component may be starting to stick.

And how comprehensive was the last service? I'd recommend checking the air filter, youd be surprised what you might find!

I checked air filter a few days ago and that was fine. i will check brakes during the weekend.

funny you should say about tires.
I read a great blog comment that some guy wrote a few years ago. ( I dont remember where or what site or what car it was Afair he was an english guy) But he had every single detail about the tires he had through the years. And how much he traveled on the wet, snow, and dry. He was able to account for every mile traveled on all his tires. What tires were the worst and what were the best. The guy was brilliant and i remember him nearly apologizing in every paragraph for being a nerd about all these stats.
But for me it was a joy to read. And f++ked if i know where to find it again.

Anyway can sensors be gone but not showing, it is a petrol renault after all:D

greasepalm

dont forget the obvious stuck in traffic while engine drinks petrol,wrong grade of oil used in engine if a newer car or remember the slick50 add run your car without oil:eek:get an emission check done to see if it is higher than normal as it should put a fault light on dash.

two wheels good

Maybe temperature sensor faulty. Thermostat faulty and not closing.
Do you have a temp guage you can monitor?

greasepalm

forgot to add if car has air con switch off

Bobo78

Spark Plugs, dirty throttle body, dirty maf sensor???

colm_mcm

Are you using the trip computer to measure?

sebastianlieken

after a drive, feel the temperature difference on the brake discs to see if one is hotter and therefore sticking
make sure you have removed dead weight from the car; boxes, coats, etc. (driving on a full taknk is + 50kg)
make sure your tyre pressures are at the recommended levels, cold vs. hot weather affects this, fill tyres when cold.

also... you havn't put on any weight lately have you?... fatty?

Johnny_Klebitz

Another possibility.

Depending on make, some cars have two engine temperature sensors.

One for the dash and the other for the engine management.

If the one for engine management goes south, then depending on the reading its sending back, the engine might think its cold and compensate by supplying more fuel. (cold cycle)

Diagnostic scan should pick this up, engine management light may not light, and emissions would be up.

Is the engine idling as normal?

Another things is are you buying your petrol from the same stations?
Petrol could have more ethanol from cheaper sources, which has 33% less energy content. EU regulations state that you can mix 10% E10 by volume into petrol, which would affect your economy by 3.3%.

How much of a drop in economy efficiency are you seeing?

Renegade Mechanic

kupus wrote: »

I checked air filter a few days ago and that was fine. i will check brakes during the weekend.

funny you should say about tires.
I read a great blog comment that some guy wrote a few years ago. ( I dont remember where or what site or what car it was Afair he was an english guy) But he had every single detail about the tires he had through the years. And how much he traveled on the wet, snow, and dry. He was able to account for every mile traveled on all his tires. What tires were the worst and what were the best. The guy was brilliant and i remember him nearly apologizing in every paragraph for being a nerd about all these stats.
But for me it was a joy to read. And f++ked if i know where to find it again.

Anyway can sensors be gone but not showing, *&*****it is a petrol renault after all:D*****

Throttle body mate:D 90% of the time, if the slight loss in efficiency is accompanied by ease of stalling the engine and a somewhat low engine speed when started in the morning, its them and they do be Manky!

Interslice

kupus wrote: »

Anyway can sensors be gone but not showing, it is a petrol renault after all:D

Make model year?

Zoney

Renegade Mechanic wrote: »

Throttle body mate:D 90% of the time, if the slight loss in efficiency is accompanied by ease of stalling the engine and a somewhat low engine speed when started in the morning, its them and they do be Manky!

Just cleaned mine, Renault Laguna, and the effect was dramatic! Very little effort too, it's surprising the difference. €10 for carb cleaner, undid two clips, removed air intake pipe, spray a bit and catch the dirty stuff by soaking up with kitchen towel (local Lidl didn't get the cheap absorbant paper for car work). I gently prodded the butterfly valve to more throughly spray around the edges, kept it up until cleaner was running clearer, pausing to let it run out. Probably helped that the tiny slope on drive meant it the dirty stuff flowed out of the body, not into it.

Remains to be seen if efficiency has improved but I'd imagine so, she's needs less power to shift her, it's that noticeable.

Edit: use heavy duty gloves if doing this, from reading sounds like the carb cleaner is nasty stuff!

kupus

Thanks everybody for all the ideas. its a bangernomics modus bought with 4/5 months of tax and nearly 18months of nct. Ecu was replaced beforehand and timing belt was just done and its lasted a full year witout any bother. Great car for the parents and i would highly recommend anyone with elderly parents to consider one. I was driving it around for a while and i had a friend in it that was able to strap her kid in the back while standing up inside, out of the rain. So even for families with kids is great. And the space in the back is massive for such a small car.
My only gripe is the 1.4 is pretty lifeless but thats a small thing as its not meant as a fly around the corners car!!

Renegade Mechanic wrote: »

Throttle body mate:D 90% of the time, if the slight loss in efficiency is accompanied by ease of stalling the engine and a somewhat low engine speed when started in the morning, its them and they do be Manky!

This sounds about right. It has recently started to stall in first when the mother drives it (but i wouldnt mind that as an indicator as she'd stall a digger) but coupled with the fact it is idling a bit funny on start up. this could be it.


Ill give this a go on Sunday. is it an easy enough job to do for a incompetent diyer?
it looks pretty straight forward. Id have no problem doing this on an older car. but these newer ones with all electrics im wary of them.
https://www.youtube.com/watch?v=02OAzLkbgwk
l

Renegade Mechanic

The 1.2 is quite different to the 1.4 and if your modus is a 1.2 itll be different to the 1.2 on that clio aswell.
Study the bottom half of these images, the location of the yellow oil cap in particular, as due to the Modus' layout you wont see the top half until a little stripping is done. Now if you look under the bonnet do you see this?(1.2)


Or either of these?(1.4)

Same engine just with cover (Throttle cable won't be present)

kupus

mine is the 1.4 2004 version

Renegade Mechanic

Good man doing the stripping, Youll have to forgive me, I thought the Modus 1.4 would use the same manifold as others. I haven't seen a 1.4 modus before:o. In any case its a similar manifold setup to newer 1.6 engines and is the easiest of the lot. The air pipe between the throttle and airbox is a bit tough to squeeze out if the others are anything to go by. The throttle body, off to the side of the engine is held on with 4x 10mm bolts and to the back is a volkswagen type connector, just push back the tab with a screwdriver gently. Then theres a pipe with a green tab that just needs to be puhed into its slot and itll slide out.

As for cleaning it, Id recommend spraying a cloth and using that to clean the body. Carb/throttle cleaner is extremely penetrative and if it works its way into the control unit through the hinge shaft, you'll be looking for a new one, (trust me ). Once the black stuff is wetted by the cleaner it will become very easy to wipe away. Good luck:D