im Axle Specialists

Technical BIG PROBLEM! fuel consumption of my croma

Currently reading:
Technical BIG PROBLEM! fuel consumption of my croma

M

Marcin89

New member
Joined
Nov 20, 2010
Messages
6
Points
2
Location
London
Guys i need some help with regards to the ridiculous fuel consumption of my 1.9 8v (ECU remapped 150bhp) Croma 55 plate.

For the past 2 months i was concerned with the amount of fuel being burnt by the croma. i have been tanking my car up to full which is around 70 litres, by doing this i was checking the computer MPG reading and my own. I was shocked that my on board comp was reading 32.5 mpg but from my calcs it turned out to be close to 16mpg. 70 litres of fuel was going in around 350miles, that is terrible:mad:

I drive very economically so this is a rather bad news, what could the route of the problem be the ECU?
 
The car would be billowing out black smoke at that rate of fuel delivery for such poor figures.
Start with the simple stuff... 50 - 60 MPH is the most economical speed in top gear, is that your driving profile or is it mostly stop- start town / city driving?

Long or short journeys?

Windows open or closed?

Air-con on or off?

Tyres correctly inflated?

Boot not stuffed full of junk?

Just you in the car or 3 / 4 / 5?

Wheel geometry good?

No binding brakes?
 
Last edited:
My driving profile is stop and start driving due to the traffic when getting to work, all the tyres are fine, air con usually off, no junk in the trunk, wheel geometry good. I usually drive in fifth around the city, would driving in 6 make a big difference?

Ffoxy said:
The car would be billowing out black smoke at that rate of fuel delivery for such poor figures.
Start with the simple stuff... 50 - 60 MPH is the most economical speed in top gear, is that your driving profile or is it mostly stop- start town / city driving?

Long or short journeys?

Windows open or closed?

Air-con on or off?

Tyres correctly inflated?

Boot not stuffed full of junk?

Just you in the car or 3 / 4 / 5?

Wheel geometry good?

No binding brakes?
Click to expand...
 
It would probably over labour the engine in 6th, possibly in 5th too based on our Croma.

Checking the brakes aren't rubbing would be an easy first check.

We have gained about 5mpg after our turbo rebuild - which wasn't 100% required but included a cleanout of the air pipes and intercooler. Perhaps breathing is an issue for yours?
 
Marcin89 said:
reading 32.5 mpg but from my calcs it turned out to be close to 16mpg. 70 litres of fuel was going in around 350miles, that is terrible:mad:
QUOTE]

70 litres & 350 miles is actually 22.7 mpg (y)

Besides the other suggestions/comments already made their is a possibiliy that you have a DPF filter related problem (assuming you have a DPF). If this is on its way out or the pressure sensor system is playing up then the car could be frequently regenerating which will drink fuel.

Only way to prove/disprove this is to use FiatECUScan/Examiner/other diagnostic kit and read the DPF regeneration statistics.

Average distance last 5 regenerations km
Last 5 regenerations average duration sec
Click to expand...
 
s130 thanks for the comment but i do not have the DPF on my car. When i calculated the MPG, the 350 miles was done by 63 litres as i took the datum point from the croma when it beeps low fuel (which is around 7 litres left in the tank).

I would like to take it to fiat but i know they will charge me an arm and a a leg to just find out the problem

s130 said:
Marcin89 said:
reading 32.5 mpg but from my calcs it turned out to be close to 16mpg. 70 litres of fuel was going in around 350miles, that is terrible:mad:
QUOTE]

70 litres & 350 miles is actually 22.7 mpg (y)

Besides the other suggestions/comments already made their is a possibiliy that you have a DPF filter related problem (assuming you have a DPF). If this is on its way out or the pressure sensor system is playing up then the car could be frequently regenerating which will drink fuel.

Only way to prove/disprove this is to use FiatECUScan/Examiner/other diagnostic kit and read the DPF regeneration statistics.

Average distance last 5 regenerations km
Last 5 regenerations average duration sec
Click to expand...
Click to expand...
 
Well that is an improvement .... now 25.25 mpg

What is a little puzzling in the large discrepancy between the self calculated and onboard computed MPG.

I suggest you try the following:

1) Fill tank to the brim so you can actually see the fuel in the filler tube just below the cap

2) Reset trim meter and also record mileage

3) Drive at least till fual level is below 50%

4) Refill to brim again

5) Note mileage, read trip distance mileage and trip average consumption

6) Check your fill-up mileage difference = trip mileage

7) Calculate your true MPG base on fill-up mileage difference and fuel added.

I always expect a small difference between the correctly user calculated MPG and the car's trip MPG but not the difference you are seeing. After 48,000 miles of correctly logging as above my Croma rarely if ever shows a difference of more that 1 or 2 mpg.

Largest difference I have seen is about 3 mpg.
 
I had a binding rear brake for a long time, which sometimes squeaked, other times didn't.

Go for a reasonably long drive using engine braking only (ideally motorways), without touching the brakes. Check that all four brake disks are stone cold after.
 
Remapping the fuel pulses can upset the on-board mpg calculations. Probably better without it, apart from the clutch issues only a careful driver can avoid.
 
Marcin89 said:
... I was shocked that my on board comp was reading 32.5 mpg but from my calcs it turned out to be close to 16mpg ...
Click to expand...

I’m inclined to trust the 32.5 av.mpg read-out over your calc. – as s130 submits, any variation by calc is unlikely to be significantly outside 32.5 ±1

My Croma (1.9/16v150) can rarely achieve 40+ av.mpg without some sustained driving in 5th or 6th. 40 av.mpg is perhaps the best achievable in 4th. At 2K revs & 60 mph I goto 5th - & at 2K revs & 70mph I goto 6th. The car can sustain 75mph (indicated) at 2K revs on a M-way. Mostly I find there’s little to be gained in going to 6th - & can do without it.

Is your problem due to your location (London) & getting enough driving in 5th (or 6th)? Can you trial it?

----------------------------
55 Prestigio 1.9/16v150 (64.8k mls)
 
Another possible cause could be your alternator being about to go. I say this from observations of my own, rather than any technical reasons! My Croma was showing only about 32mpg. I had put this down to a myriad of short journeys and the fact that the service was due that month.

After servicing the MPG rose slightly... but not much! Then the alternator went, 10 days after my timing belt was changed and the service done. MPG now seems to be around 38mpg (urban). I drive a 1.9 16v JTD.

Might be worth getting that checked as well?

HTH
 
Marcin89 said:
s130 thanks for the comment but i do not have the DPF on my car.
Click to expand...

I would have expected your Croma to have a DPF, unless removed.

If it has a DPF then it's probably the fuel pressures and pulses being altered that is causing the trouble. Also failure to reset the oil life mileage will do this. Remaps will often result in false mpg figures from the on board computer, usually showing an apparent improved mpg after a remap.
Just reset my service mileage after 2 oil changes where the garage cannot reset it. Fortunately only done 13000 miles in 3 years, so had 7000 left before troubles.
 
Caravadossi said:
I’m inclined to trust the 32.5 av.mpg read-out over your calc. – as s130 submits, any variation by calc is unlikely to be significantly outside 32.5 ±1

My Croma (1.9/16v150) can rarely achieve 40+ av.mpg without some sustained driving in 5th or 6th. 40 av.mpg is perhaps the best achievable in 4th. ----------------------------
55 Prestigio 1.9/16v150 (64.8k mls)
Click to expand...

Very similar to mine:

In 48112 miles: Best MPG = 43.32 ; Worst MPG = 26.16 ; Ave.MPG = 35.07 (6236 litres / 1371.92 gallons of fuel)

Note: 14606 of the above miles done towing a 1000kg caravan.

I've always kept very accurate logs of every drop of fuel and money put into the tank on all cars I have ever owned, together with exact mileage and if the tank was filled to top or not.

Now how sad is that? :yuck:
 
Well thats great, i just got a check engine light come up on the croma. Mechanic checked it to be the DPF needing resetting.

Thats a kick in the balls, as i always thought i dont have a DPF. The diagnostic comp said to run the engine at 3500 rpm on idle for 12 minutes to clear the problem. HAHA dont want to do that or i may snap the belt.

Could this be the problem of my fuel consumption?
 
Your fuel system has been compromised by a remapper, get him to remove it and refund. I thought most of them had learnt how to do this by now.
You need to get the temperature of the exhaust system up by driving down a motorway, but with the remap it's still upsetting the DPF regen. Plenty of info on www.alfaowner.com, although on the twin cam 150 HP version.
Did I suggest you had a DPF? I think it was a requirement on diesels introduced after a certain date.
 
I personally think the days or engine ECU remaps are soon coming to an end except in special cirusmstances or for motor sport where other radical changes may have take place and longterm running, reliability and cost are not an issue.

New MOT regulations (EU wide) will in the next few years fail ECUs that have been remapped by any change not officially issued via the manufacture. Very easy to test these days. Just requires manufactures to provide ECU checksums etc. In this day and age, especially as UK MOTs are computer based, not a big problem.

Between now and then I think the more obvoius driving thrust is that modern Euro V (and beyond) emission regulations are making engine managment systems, DPFs, CATs etc. far more complex and far more "closed loop integrated" so much so that tweeking one parameter can have massive effects in other areas. Venturing down this route could prove very expensive with regards to repairs etc. and those companies that can correctly make these changes will be few in number and in addition to their development costs will be able to demand far far higher prices.

So a £250 ecu remap will rise to £1000+
 
s130 said:
I've always kept very accurate logs of every drop of fuel and money put into the tank on all cars I have ever owned, together with exact mileage and if the tank was filled to top or not.
Click to expand...

FYI
I've done exactly the same for many a year. My Croma (1,9 Multijet. 150 BHP. Built 2008. Owner since 2010) consumed over a distance of 18225 km or 11327 miles 1 liter on 15.3 KM or traveled 43.14 MPG. I didn't tow any vehicle, am a modest driver on 70% dual carriage way's or motorway's and 30% urban. If I compare to other cars I've owned, Croma classic and Marea 2.4 10V, all derv drinkers, I am not dissatisfied.
 
You must log in or register to reply here.

Similar threads

L
Technical Croma oil leak
Replies
4
Views
127
Landrange
L
A
General Fiat croma new springs
Replies
0
Views
136
Alin0423
A
JavaChri
Technical Fiat Croma cluster can bus ids
Replies
0
Views
196
JavaChri
JavaChri
D
General Whats the ultimate Croma a 2.4 Prestigio worth now ?
Replies
0
Views
258
davidthelodge
D
Soufianejoe
Technical Gearbox and steering problem
Replies
3
Views
82
bugsymike
B
Back
Top