Diagnosing High fuel usage

Diagro

Diagro

Diagro

Soldato
Joined
3 Jun 2012
Posts
11,261
Hey

So i am trying to diagnose the cause behind the fact my Clio 172 is useing too much fuel.

I have replaced the Precat Lambda as it was reading incorrectly which helped but still uses too much.

Belt Timing is correct as the garage who fitted it along with AUX kit and dephaser checked yesterday and said it was perfect.

No fuel smell, so no leaks.

I'm leaning towards Injectors being at fault, maybe dribbling or something?

What would you all suggest i check next before i start replacing injectors >.<
 
Have you checked for binding brakes?

Sometimes it's not noticeable from the driving seat, but manifests itself at the pumps.....
 
Mpg ranges from 19.7 to 28 over last 5 to 6 fill ups.

breaks may be slightly binding but that would show on the mpg counter which is in fact showing far above 35 all the time.

Rear breaks spin freely when jacked up and break off.

Garage who checked timing said anything could be cause it. And mentioned injectors.

Just trying to get an idea of what I can check next to try and solve this problem I have
 
Any idea (or could you ask someone to see) what the fuel trims are like?

Coolant temperature sender showing a low reading when the car is warm is another thing to check out, that usually results in the car running too rich. Can cause hot start issues but not always.
 
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I have the RS tuner box I can plug into the clio.
Will that tell me the fuel trims?

Coolant temp sensor is fine. Reads between 80 and 90 on a trip home.
But saying that it might be reading too low and the engine be warmer?
 
So you're saying the actual fuel runs out before the computer says it should?

I'm confused by your;

Mpg ranges from 19.7 to 28 over last 5 to 6 fill ups. ... mpg counter which is in fact showing far above 35 all the time.
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MooMoo444 said:
So you're saying the actual fuel runs out before the computer says it should?

I'm confused by your;
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Trip computers (at least in the cars I've had), don't actually calculate distance/fuel for averages. They seem to use a pre-programmed conversion based upon the amount of time spent at certain MPGs (which themselves may be made up based on a pre-programmed formula)
 
Diagro said:
Mpg ranges from 19.7 to 28 over last 5 to 6 fill ups.
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Short or long journeys?

I do a 4 mile commute daily, a few miles here and there through the week but nothing major. Average MPG for these short journeys is normally sub 25.

I'll see anything up to 35-40MPG if I don't go lead-footed on the motorway.

2002 172 btw.
 
I would first give it a service, clean the MAF, check the ignition and give it a good run.

Water temp sensor could be an issue.
 
That would be my first question too - is that motorway running or around town? If it's around town and you like the loud pedal (even if you're not redlining it everywhere) it might be about right.

It's not normal for the OBC to be that far out though - normally around 10-12.5% max in my experience
 
I've got a 160bhp golf 1.4 petrol GT. I do town driving and give it the beans every now and then. I get around 24-25 solid mpg.

So, sounds about right
 
fastwunz said:
I've got a 160bhp golf 1.4 petrol GT. I do town driving and give it the beans every now and then. I get around 24-25 solid mpg.

So, sounds about right
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Christ, I used to get 34 out of my 1.4 170 brake mito and I drove it like a loon! Suppose it's a slightly smaller car though.
 
my old car (FiestaST Mk6) dropped from 30s to the 20s over winter and it took me quiet a while to realise that my temp was a tad lower on the gauge. Being a tad lower on that = 50-60c temp instead of 90-95c, hence poor mpg. Maybe check that.
 
Overlag said:
my old car (FiestaST Mk6) dropped from 30s to the 20s over winter and it took me quiet a while to realise that my temp was a tad lower on the gauge. Being a tad lower on that = 50-60c temp instead of 90-95c, hence poor mpg. Maybe check that.
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Either your journeys were so short that the engine never warmed up properly, or your thermostat is not closing fully. The whole point of having a thermostat is to regulate the engine temperature.
 
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