Up until about 4 weeks ago my 04 1.6 did around 33-35 average MPG over the course of a full tank. Increasing to around 38ish if I did lots of motorway work, and dropping to about 30ish if I was driving it hard.

But now, it’s around 24-27mpg even when driving steady and with lots of motorway, as such I’m only getting about 330 miles out of a tank compared to 400+ before!

What could be causing this? I have recently changed:

Cleared the air filter (only 4,000 miles old anyway)
Changed the oil and oil filter (using Castrol Edge before and after)
New spark plugs
Had a Fiat dealer change the cambelt
Had a Fiat dealer clear the ‘Service Due’ message
Changed brand of fuel

But none of this has made any change. I can’t remember any warning lights ever coming on and the fait dealer never said anything about any errors stored in the ECU.

The car drives fantastic, with lots of power and no problems.

Anyone got an idea why the MPG might have dropped so badly, and how to fix it!?

Cheers
Matt
:worship:

Could be the timing slightly out when the cambelt changed. Only by a tooth or so. Could also be the new fuel? Where did you get it from?

Alan

Sounds like my 1.6 ..have you got a heavy right foot since you fitted the induction kit Matt :devil:

a1ant said:

Could be the timing slightly out when the cambelt changed. Only by a tooth or so. Could also be the new fuel? Where did you get it from?

Alan

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Nope, it started happening before the cambelt was changed. Alos, the car feels just as it did before and after the new cambelt.

Cheers

PNL said:

Sounds like my 1.6 ..have you got a heavy right foot since you fitted the induction kit Matt :devil:

Click to expand...

Hehe

It was still in the low 30s with the induction and remap!! So I dont have a clue whats going on! :bang:

:worship:

I think the MAP sensor is a favorite for this :chin:

If it's only slightly out then it wont show an error and yet still the car performs well (as you'd expect when drinking fuel )

Also watch for large toe errors which can bring down mpg (not to mention your tyres )

More cold starts? More use of headlights/heated screen/fan etc due to colder weather?

Argonought said:

I think the MAP sensor is a favorite for this :chin:

If it's only slightly out then it wont show an error and yet still the car performs well (as you'd expect when drinking fuel )

Click to expand...

I did the map sensor on mine ..and it didnt do anything ..zilch nada ..I have got a right foot with leaded soles tho :devil:

Disclaimer .. Its not my fault honest :shrug:

Hummm....Map sensor you say? Whats that then?

How much is it, and can I fit it without rebuilding my engine!?

Cheers

Go for the no cost, easy checks first.
Unhitch the caravan and remove the roof rack


TYRES AND BRAKES
Tyre pressures make a huge difference as does tracking and brakes binding, so check your tyres pressures, look at the tyre surface for signs of alignment problems and make sure the car rolls easily on a very slight slope

IS IT AN INCORRECT READING?
Are you actually putting in more fuel than usual?

LAST WORK DONE
Are you 100% cast iron sure the mpg plummet didn't happen at the same time as the cam belt was changed?

I think the map sensor always seems to be the fall guy when things go wrong on the 1.6 I remember it came up on mine in a diagnostic when it wasn't to blame at all and the problem lay with a faulty injector and inlet manifold air leak ..sensors are currently £78 +vat and postage on shop4 parts at the moment and can be an expensive change if its not the problem

Big mistake if it's not faulty as you say Phil.

I notice Decks is now paranoid about cam belts ever since his 1.6 actually ran better after his was changed.

I was half expecting my JTD to run better after having a new belt fitted but, like MF-Racing, mine runs exactly the same as before

Yes I too think the MAP sensor is often not guilty of accused crimes. Mine had a MAP sensor fault code triggered after i was messing with the aircon linear sensor as they are on the same sort of 5v reference circuit. Once i'd removed the fault code again it was fine.

Why was I playing with the linear sensor? Because my air con ceased to function after my cambelt change? Why was that? Cos they had knocked off the aircon compressor connector. Duh!

The thing is that the synching of the camshafts and crank (as needs to be done on a cambelt change) only need to be a mere degree adrift for big changes in running and economy

ive noticed somethng similar with my 1.6.. 44 mile run to hull at 70 i used to average about 38-39mpg..

but recently only getting 32-34mpg... all i could think was cold weather

only other reason for mine i can think is possibly going to 18" alloys from 15" alloys.... all balanced perfect though.... and same rolling diametre...

italian style tune up??? give it a good run

(has anyone ever had a problem with mpg and fuel along the lines of ron 98 or v-power??)

Deckchair5 said:

Tyre pressures make a huge difference as does tracking...

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Four wheel tracking check would be at the top of my list... 2 Stilos (1.6/JTD), 30 months and 52K on...

Has your commute or daily driving changed? I know mine has involved much more stop start driving since the schools went back, combined with the cold weather im sure it all adds up!

Right, caravan unhitched and handbrake taken off

Did a 200 mile round trip yesterday, 95% motorways, going really steady and it returned a average of 27.6mpg

Just checked the tyre pressures, all ok and still the same as they were last month.

As far as I know the tracking is still ok, had 4 wheel alignment done about 3 months ago and it was spot on then, still feels like its ok and no strange ware patterns on the tyres (all new Goodyear's)

Yep, 100% sure that it happened before the cambelt change as I was hoping when they plugged it into the computer at the dealer it would clear any faults and fix it.

I haven’t checked how much fuel I’m putting in, but I’m 100% sure that I’m not travelling the same distance as before, before needing to fill up. I travel on the same roads everyday to and from work and the fuel is not lasting as long.

So, this MAP sensor. Anyway to test it out to see if its doing what it is supposed to be doing?

:idea:

Deckchair5 said:

Go for the no cost, easy checks first.
Unhitch the caravan and remove the roof rack


TYRES AND BRAKES
Tyre pressures make a huge difference as does tracking and brakes binding, so check your tyres pressures, look at the tyre surface for signs of alignment problems and make sure the car rolls easily on a very slight slope

IS IT AN INCORRECT READING?
Are you actually putting in more fuel than usual?

LAST WORK DONE
Are you 100% cast iron sure the mpg plummet didn't happen at the same time as the cam belt was changed?

Click to expand...

Unless you were doing a steady 90 then that consumption sounds really dire.

Don't own a 1.6 but I believe you can just unplug the sensor which then reverts to factory settings. If your consumption actually improves then the case is proven (you'd expect consumption to get worse with default settings)

Decks, as usual, will know the answer

Argonought said:

Unless you were doing a steady 90 then that consumption sounds really dire.

Don't own a 1.6 but I believe you can just unplug the sensor which then reverts to factory settings. If your consumption actually improves then the case is proven (you'd expect consumption to get worse with default settings)

Decks, as usual, will know the answer

Click to expand...

Tell me about it!

I dont think I once went over 75mph as well!

Cheers

Do you race through the gears and take the revs upto the limit before you change gear ..or as I put it drive enthusiastically ..or do you drive through the gears like a granny on a picnic ..smack your wrists if you do the later