Alfa Romeo Forum banner

147 1.6TS Poor fuel consumption?

9K views 31 replies 6 participants last post by  Dex87 
#1 ·
Hi All,

I've had my 147 for just over a week now, and loving the cornering abilites, but not enjoying the fuel bill so much!
It's early days yet, but I only seem to be averaging 26-27 MPG, is that normal, or is something wrong? I was expecting at least low 30's...

Also, it seems to have bugger all power/torque at the low end of the revs. Once the revs get above ~4.5k it goes great, but below that it seems a bit flat.
I haven't driven any other 147's so it's hard to tell, but based on similar power/size cars I've had previously I would have expected a bit more grunt at the low end.

I'm thinking it might need the O2 sensors replacing, but I'm a bit hesitant seeing as there's 3 of them!
 
#2 ·
lambda's well usually issues at cruising speeds but diagnostic on ecu can show results...........as for economy depends on how you use loud pedal

ps 2 lambda on manifold are sensing and 3rd is diagnosing only person with software will know if they are switching right and are not cheap for bosch units
 
#3 ·
Hi skov, I have a 1.6 twinny and yes they are a bit low on torque at low revs, the answer is to drive it like you stole it :) they do come alive at the top end. This does effect mpg though, I have had mine a year and averaged 29 mpg according to the onboard computer.
Is you temp getting up to 90? if not you could have thermostat problems which would put your mpg down.
 
#4 ·
I'll be disappointed if I can't average over 30mpg :(



I had my ODB tool attached to the car on my drive into work this morning to see if I could spot anything.



Whilst sat in traffic at idle I had a look at the O2 sensors.

The two pre-cat sensors are both switching from 0.1V to 0.6/0.7V.

They're switching a bit slower than I would expect, maybe about once every 2 seconds - is that normal for an Alfa, or should they be quicker than that?

The post-cat sensor doesn't do an awful lot and seems to sit between 0.4 and 0.5V for the most part.



My long term fuel trims are +5% on bank1 and +6% on bank2, which doesn't seem ludicrous.



Idle speed is ~850 RPM when warm.



I got a couple of snapshots of the MAF reading at different RPMs, do these seem normal?



850 rpm - 2.75g/s

3045 rpm - 20.25g/s

5622 rpm - 37.25g/s



The temp gauge in the dash gets up to about 90 degrees within a few minutes, dips briefly (presumably as the thermostat opens), then creeps back up to just below 90 degrees and stays there, steady as a rock.

Interestingly, the temperature reported by the scan tool takes much longer to get up to 90 degrees, and was reading 10 degrees lower than the dash gauge for the first 20 minutes or so of my journey. It eventually caught up with the gauge and agreed with it though!

Does the 147 have 2 temp sensors, one for the ECU, and one for the cluster by any chance? or is the gauge in the dash frigged a little bit?
 
#7 · (Edited)
lambdas seem to be lean part of graph IMHO as for post cat its saying your cat is good with no issues
if your car runs lean it will affect your fuel consumption negatively but seek advice
check your pipe between throttle body and MAF for splits as well.......ie take it off and check properly:thumbs:

any fault codes logged?
 
#6 ·
I ought to do a more definitive test like brimming the tank really :) never reset the computer thingy since I bought it, I will try resetting it at the weekend. I haven't been able to FES on the car to check my lamba readings against yours skov, I will post when I have.
 
#8 · (Edited)
I'm pretty &nal about monitoring my fuel consumption, I always brim it and note down how much I've put in and how many miles I've travelled. I've got a spreadsheet containing every fill up in each of my cars for the last two years, sad I know :rolleyes:

The trip computer thing seems pretty accurate on mine, it's average reading is within 1MPG of my calculated value.

One thing I have noticed is that if I start cruising at a fixed speed, the trip computer 'actual reading' starts off reporting a really crap MPG, but it very very slowly creeps up to something fairly respectable.
It takes maybe a mile or two before it settles at a decent reading, which again leads me to believe the lambda sensors might be degraded and switching too slowly.
What's really scary though is that the reading drops to single figures if I cane it, I saw 6 MPG on it at one point :eek:
 
#9 ·
I'm pretty &nal about monitoring my fuel consumption, I always brim it and note down how much I've put in and how many miles I've travelled. I've got a spreadsheet containing every fill up in each of my cars for the last two years, sad I know :rolleyes:

The trip computer thing seems pretty accurate on mine, it's average reading is within 1MPG of my calculated value.

One thing I have noticed is that if I start cruising at a fixed speed, the trip computer 'actual reading' starts off reporting a really crap MPG, but it very very slowly creeps up to something fairly respectable.
It takes maybe a mile or two before it settles at a decent reading, which again leads me to believe the lambda sensors might be degraded and switching too slowly.
What's really scary though is that the reading drops to single figures I cane it, I saw 6 MPG on it at one point :eek:
normal that in my eyes regarding computer:thumbs:
 
#14 ·
Hi skov, my lamba sensors are pretty much exactly as yours are reading, couldn't do my maf unfortunately as my laptop battery has decided it will hold a charge for about 5 minutes :(
Dash temp gauge sat at 90 but actual temp off FES went from 86 to 97 when fan kicked in and back down to 86. Will charge my batts and attempt maf tomorrow :lol:
 
#16 · (Edited)
Hi skov, got some air quantity readings off my 1.6 twinny today,
850rpm - 13kg/h ------ 21.6g/s
2000rpm - 24kg/h ------ 40g/s
3000rpm - 36kg/h ------ 60g/s
4000rpm - 50kg/h ------ 83.5g.s
took them whilst in neutral so no load on engine.
 
#19 ·
Ahhh yes I now realise my figures in second column should really be g/minute so..
850rpm--------0.30g/s
2000rpm-------0.66g/s
3000rpm-------1.00g/s
4000rpm-------1.40g/s
Does that make more sense :confused:
Cheers Rockhoper.
 
#20 ·
I think you're still out by a factor of 10, lol

I think it should be:
g/s = kg/h * 1000 / 3600

Which gives:
850 - 3.6 g/s
2000 - 6.6 g/s
3000 - 10 g/s
4000 - 13.9 g/s

I've just taken some readings in neutral on mine:
850 - 3.00 g/s
2000 - 7.00 g/s
3000 - 9.75 g/s
4000 - 14.00 g/s

I think that's close enough to say they agree!
 
#28 ·
i think this is immaterial as engine needs to be underload to as airflow is some what drastically increased
i may think op may have a MAF problem and we are reading to deep into it,by all means clean throttle body but dont physically move butterfly by hand ,take it off and spray but leave butterfly alone as you can alter spring tension and youll have more problems than you started with :thumbs:
 
#21 ·
My head hurts :confused:
I thought they seemed a bit low, I even googled the weight of air :lol: it seems 1 cubic foot = 28.32 litres and weighs 38.7g
 
#22 ·
You learn something new every day :D

Incidentally I had to drive my wife's 'orrible french 7-seater earlier.
Checked her trip computer and it says she's averaging 35mpg - that's with a similar power 1.6 petrol engine in a car that weighs 250kg more and has the aerodynamics of a brick.
I'm not happy :cry:
 
#23 ·
I reset my computer yesterday, (hold the set on the stalk in for a few seconds)first time it has been reset since I've had the car, 11 months, only done 20 miles since but the average consumption now reads 36.6 :confused: it was under 30 before.
 
G
#26 ·
Is the idle rock solid at 850-ish rpm or is it fluctuating? 750 -950 rpm once warm?
You mentioned in your OP that it doesn't wake up until 4,500rpm and higher?
does it seem to be gradual below that, hold the revs then increase onwards all of a sudden after that?

If it is, remove the induction hose, clean the throttle body thoroughly, plenty of "how to's" on here and pay attention to the difference between CF2/ CF3 proceedures....
Inspect the bellows for any tiniest of splits from the maf to throttle body and refit.

Remove the MAF multi_plug connection and check the pins, are they nice and clean? Spray with electrical contact cleaner and refit.

Do the same now to the O2 sensor connections.
Check your earth straps, paying attention to the ECU one in particular,the NEG battery earth to inner wing body & gearbox earth. Remove, clean, refit.

Do a soft ECU reset (miracle cure).
Now take it for a good spin of 25 miles + and you will see it should return what you are expecting.

Never completely rely on ODBII codes to tell you everything, they dont....! Listen, Feel and go with Gut Instinct and common sense too:thumbs:

Or... You can continue reading codes till the cows come home and ignore the above, your choice:thumbs:
 
#27 ·
Hi Grahameo,

Good point on the ODB codes, it's easy to become too reliant on them and forget about the basics!

Idle is rock steady 850 when warm.
"does it seem to be gradual below that, hold the revs then increase onwards all of a sudden after that?"
I think I'd say yes to that.
I'd also say there's a very slight roughness at high revs when it does get going.

I'll get cleaning and report back :thumbs:
 
G
#29 ·
No problem matey..
Forgot to mention that over the years you ar bound to get tiny splits in the rubber belows, its rubber and it perishes with time.
A handy tip is to us some elstic bands and three latex gloves to cover the orifices then dump it in a sink under warm water... Any leaks will be apparent. If water can get inside the air can leak!
Its not the end of the world if it is leaking, I know how much Alfa charge for them! So......

A further handy tip is to have a bicycle repair kit handy.... The tube of vulcanising glue is what you need, rubbed between the splits and a clothes peg to hold it together for 15 mins is all you need... job done. Test it again in the warm water to make sure :thumbs:
The vulcanising fluid will make the area stronger than it was before the split!!!
No need to spend a fortune:lol:
 
#30 ·
Great tip on checking the bellows :cool:
I gave it a go, and I didn't find any leaks.
I've also cleaned the contacts on the MAF, O2 sensors, and coolant temp sensor (the MAF ones did look a bit dodgy).
Next job is the earth straps - where is the ECU earth strap? In fact where is the ECU???
 
#31 ·
I think I can bring this to a close now.
Cleaning the earth straps etc didn't seem to make any difference.

However after changing the two front O2 sensors I'm now averaging 32.5 mpg on my commute (half of which is sat in traffic), and over 35mpg on a long run.
Not fantastic, but a lot better than the 26-27mpg I was getting :D
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top