Author Topic: Cannot figure out why my Jazz MPG is so bad  (Read 3565 times)

hugh650uk

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Cannot figure out why my Jazz MPG is so bad
« on: November 19, 2018, 03:34:39 PM »
Hi guys!

I recently bought a 2007 Jazz SE 1.3/1.4 iDSI CVT from a friend of mine who had the car for 2 years, he went for a brand new jazz and sold me this one for almost nothing. I don't know much about the history of the car nor does he, apart from it was a cat C at some point, last serviced Nov 2017 (I'm servicing the car very soon), using oil 0w30 synth, air con dead, brakes were binding a bit, engine had a code for cylinder 4 misfire and a warning for running rich. As the car was cheap I thought it was worth the hassle.

Basically I fixed all the problems and engine issues, got new sparks in, changed 2 coils, clean the rest and swap them round. all the codes cleared and so far the engine has been fine. Also got my mechanic to check the engine and gearbox and he assured me they are in good shape. An gearbox specialist also checked the CVT and he also said it is good! Car also passed the MOT without any problems.

So I started driving the car as my daily, everyday I do 6 journeys of 4 miles each, I know this is not the best scenario for good MPG specially because the car has time to cool down between trips, but since I started calculating it, when I'm just driving around London, the Jazz is doing only 26 27 mpg which to me sounds extremely poor. About 250 miles range from a full tank. If I do the same with my Panda I can easily get 38-40, unless the weather is really really cold.

Anyway, the problem I'm having is that I don't know where to look from here and I can't afford to pay Honda to scan the car (150). Before I could blame the binding breaks, engine issues, but since I got all sorted I don't know what else to look for. The car seems to have the power it should and the MPG improves on the motorway. Done a round trip to Guildford with 4 adults in the car, going 65 70 mph most of the way and got 48 mpg. Last Saturday went to Birmingham and back, 2 adults, again going 65 70 mph, also tested a bit and car reached 85 without much struggle, in the end I got 53 mpg. These are actual mpg, not the trip computer, for some reason the trip computer is very optimistic in town and really conservative on the motorway.

The only strange thing I can see from scanning the ECU with Torque is that the engine load is always high, like if the car is idling and in neutral the load is at 34% and sometimes engine load simply stays off-line. But I don't know for sure if the Jazz has a load sensor or if this is a calculated number. Still strange I think.
 
Does anyone have an idea of what could be causing such poor mpg?

Big Thanks!
Hugo

richardfrost

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #1 on: November 19, 2018, 03:58:41 PM »
Did you change all 8 Spark Plugs - assuming it is the same as my manual car. Surprisingly, given their location, quite a lot of people don't realise there are 8.

Otherwise, I would say it is down to the stop start nature of your daily routine, although I would still expect you to be reaching the low to mid thirties. Maybe try a bottle of Redex in your next refill? Full bottle in an empty tank and then fuel up to the brim.

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #2 on: November 19, 2018, 05:31:19 PM »
Yes, all 8 changed for new NGKs factory spec and I checked the gap as well, what a pain the back ones are, but done it for sure!!

What I find strange is that my friend used to use the car for short trips as well and he claims the fuel economy was great, although he does not measure full tank to full tank like me, he is more like how far a 20 can get him, so hard to compare.

The only thing I can think of is this load sensor always with a high reading, if it reads more load than the actual load, I guess it would send more fuel to be burned, no?

Is there an actual load sensor?

Cheers

peteo48

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #3 on: November 19, 2018, 05:33:56 PM »
Just to say, in agreement with Richard, that low to mid thirties might be about right. I do a lot of short stuff in traffic and my lowest mpg on one of my Mk2 Jazzes was 33 mpg during winter.

Hope you get it sorted.

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #4 on: November 19, 2018, 05:38:35 PM »
Yep, anything above 30 mpg I wouldn't worry too much, as I know the way I drive does not help, but below 30 seems too much for such a small engine.

MicktheMonster

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #5 on: November 19, 2018, 10:02:55 PM »
Hi Hugh, I've got a 2003 manual 1.4, about town I get an odometer reading of mid-thirties.

If you take a bit off that for error in odometer (as you are quoting actual mpg, mine is a fairy tale), a bit more for a auto gearbox, possibly more again as you drive round London and I drive round a small town in Norfolk so probably have less stop/start going on, possibly adjust for condition of vehicle or driving style and our figures aren't too far apart.

Your mpg on a on a longer journey is about rigbt, so it's obviously able to work properly in the right conditions, it may pick up after a service, it's also worth taking 5 minutes to check your air filter to ensure its not struggling to get air in.
« Last Edit: November 20, 2018, 12:40:34 PM by MicktheMonster »

springswood

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #6 on: November 20, 2018, 09:49:31 AM »
Just going from what I've read here I should think there is still hope for improvement. The EGR valve sticking open is a common one and easy to fix. Mine was duff but with similar journeys to you I still got mpg in the 40s.
Don't know about a load sensor but there are two oxygen (lambda) sensors in the exhaust before and after the cat. Again I understand cleaning these isn't difficult provided you can get under the car.
So worth looking some more on here about those. Good luck.
"Indecision is a terrible thing"
Or is it? What do you think?

olduser1

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #7 on: November 20, 2018, 12:10:56 PM »
Its the cold weather + short journey, I would just enquire of the prev owner about fuel they put in each week month.
Try a full tank of Shell V power or BP super stuff.

bill888

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #8 on: November 20, 2018, 12:35:12 PM »
As pointed out by olduser1, your problem sounds like a combination of short journeys and colder temperatures.
I don't know if it makes a real difference but when was the CVT oil last changed ?
The fuel economy of an auto is also likely to be worse than a manual, particularly when driven around town imho.

fwiw, I still run a 57 CVT which is only used for short trips less than 3-4 miles each way around town.  The dash claims 30-33mpg (I reset the trip meter at each fill up), but I know the actual mpg is about 10% lower when filling up at the petrol station in the past.   




« Last Edit: November 20, 2018, 12:40:03 PM by bill888 »
2007(57) Jazz 1.4SE CVT-7 (GE3 - made in China)

bus_ter

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #9 on: November 23, 2018, 01:56:22 PM »
Your figures are inline with mine and normal IMHO.  I wouldn't worry.

nigelr

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #10 on: November 24, 2018, 12:33:14 AM »
If it helps, I have had two Jazzes and my MPG always fell (and falls) dramatically during winter - short journeys, heater, lights, etc. I bought my Mk2 in August and had it fully serviced at my local garage - the MPG immediately rose 5mpg or so after new plugs, filters and oil.

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #11 on: November 26, 2018, 08:41:06 AM »
As pointed out by olduser1, your problem sounds like a combination of short journeys and colder temperatures.
I don't know if it makes a real difference but when was the CVT oil last changed ?
The fuel economy of an auto is also likely to be worse than a manual, particularly when driven around town imho.

fwiw, I still run a 57 CVT which is only used for short trips less than 3-4 miles each way around town.  The dash claims 30-33mpg (I reset the trip meter at each fill up), but I know the actual mpg is about 10% lower when filling up at the petrol station in the past.

CVT oil was changed by Honda just before I got the car from my friend. So that shouldn't affect negatively.

You basically described the mpg situation of my Jazz  :) Good to hear that!

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #12 on: November 26, 2018, 08:42:50 AM »
Your figures are inline with mine and normal IMHO.  I wouldn't worry.

Thanks for the info!! That helps a lot to put my mind at ease!!!  8)

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #13 on: November 26, 2018, 08:47:30 AM »
If it helps, I have had two Jazzes and my MPG always fell (and falls) dramatically during winter - short journeys, heater, lights, etc. I bought my Mk2 in August and had it fully serviced at my local garage - the MPG immediately rose 5mpg or so after new plugs, filters and oil.

Yep, I do realise that the way I drive + the nice weather now will definitely not help, but I always heard great things about the Jazz that I was a little bit shocked with the mpg  :o, I was expecting something around 40mpg around town, but as long as my Jazz is not burning fuel out of control, that is what matters!!!  ;D

hugh650uk

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Re: Cannot figure out why my Jazz MPG is so bad
« Reply #14 on: November 26, 2018, 08:49:40 AM »
Just going from what I've read here I should think there is still hope for improvement. The EGR valve sticking open is a common one and easy to fix. Mine was duff but with similar journeys to you I still got mpg in the 40s.
Don't know about a load sensor but there are two oxygen (lambda) sensors in the exhaust before and after the cat. Again I understand cleaning these isn't difficult provided you can get under the car.
So worth looking some more on here about those. Good luck.

I will soon service the car and will also clean the EGR for sure!!! Hope it will bring improvements!!

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