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Poor fuel consumption

flyerphil

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Location
Derbyshire, United Kingdom
Car
2002 Honda Accord SE
I have suspected poor consumption for some time. :mellow:

This past few days, I did a trip to Scotland. I did 570 miles and used 77 litres of fuel - ie around 34 mpg. The car runs fine - starts, idles, runs ok. The tires were pumped up, the air filter is clean, the plugs are reasonably new, and I used the cruise control there and back - mainly motorways and no serious traffic delays.

My previous Accord on a similar journey, would return 40 mpg - Ok 39.4 to be accurate.

So there is something wrong. Its using 15% more fuel.

I know it could be anything in the fuel metering, sensors etc. Difficult to diagnose. Has anyone any experience with this, suggestions etc.

Thanks
 
Has the car always been like this since you got it, and if so, how many previous owners, how long have you had it, which engine is it, how many miles has it done ?
 
As what Brian said
 
If I recall correctly, similar threads have fingered the O2 sensor(s), although often along with rough idling (you say yours is OK), at 80 to 100k up. How many miles on yours and anything to note in the service history?
 
In answer to your questions, have had the car for around 10 months. It has 110k miles and a full history with 3 previous owners. Its a 2 litre - like my previous one. Except this one is a post face lift; the other was pre face lift.

It idles smoothly. Passed its MOT first time.

The only thing I have noticed different between the two, is that this one is bit more noisy when cold. Fine when it warms up. I did check the valve clearances when I got it but they seemed OK.
 
Apart from the petrol that's been put into it by the previous owners (I've always been dubious, but I am beginning to believe claims about Shell V Power etc), the only other thing that will make a difference on that scale is the tyre brand and tyre pressures.
 
Very slightly binding rear brake? Check the rear wheels for heat/smell when you get out after a journey that's more than a few miles.
 
freddofrog said:
Apart from the petrol that's been put into it by the previous owners (I've always been dubious, but I am beginning to believe claims about Shell V Power etc), the only other thing that will make a difference on that scale is the tyre brand and tyre pressures.
I would agree that if tires are under-inflated, then this does affect consumption. However recently a trial was done in which the tire pressure was set to that recommended versus inflating up to 40 psi and no difference (within experimental error) was noted.

I have never experimented with fuel - except for diesel. When I had a diesel, I found Jet gave a noticeable increase, but bio diesel was very poor.

Since with an injected engine, the fuel metering depends on inputs from various sensors, to the ECM, which then injects fuel in the correct amount - then since the software algorithm is fixed, then if say each sensor was at its limits of tolerance, then conceivably this would account for differences between two cars of the same model with identical set up.

After more research, some owners report 40 mpg on a run (using brim to brim) others only 34, like me, across the two cars I have owned. I suppose you would have to replace all the sensors for new ones to check this theory.

I'm not sure that tire brand makes much difference. The rolling resistance is a small effect for correct inflation.

I suppose I just have a bad'un, ie one of my sensors is out of limits.
 
flyerphil said:
I would agree that if tires are under-inflated, then this does affect consumption. However recently a trial was done in which the tire pressure was set to that recommended versus inflating up to 40 psi and no difference (within experimental error) was noted.
I'd like to see references to that trial, I find it hard to believe, after all, rolling resistance for cars is no different than for cycles, and cycle tryes also have a range of inflation. Take the tyres to max, and it's a heck of a lot easier to pedal.



flyerphil said:
I have never experimented with fuel - except for diesel. When I had a diesel, I found Jet gave a noticeable increase, but bio diesel was very poor.
I too have always been sceptical, but I have recently changed my mind. I have had my 7th gen 2.4 since Jan 2006, and I have never got more than 30 mpg, even though I have tried very hard on a couple of occasions. In the 85k miles i have always put 95 RON into it, almost always Tesco. I'm not using the car at the moment (it's SORN) but when I do, I intend to over-inflate the tyres and go to Shell V Power to see if it makes a difference.




flyerphil said:
Since with an injected engine, the fuel metering depends on inputs from various sensors, to the ECM, which then injects fuel in the correct amount - then since the software algorithm is fixed, then if say each sensor was at its limits of tolerance, then conceivably this would account for differences between two cars of the same model with identical set up.
It depends on how the engine works. I don't know about the engine in your car, but in the K24 there is a knock sensor, and the ECU advances the ignition until knock, and then backs off a couple of degrees. This will make a difference to mpg with different fuels.



flyerphil said:
I'm not sure that tire brand makes much difference. The rolling resistance is a small effect for correct inflation.
Tyre brand makes a huge difference to mpg, if you check all the alternatives for the sizes that you have at the moment, you will see a big difference in the "economy" ratings for each brand.




flyerphil said:
Think I will replace the oxygen sensor. They are not that expensive and do degrade over time. Its recomended to replace them at 100k anyway.
I can't comment on the engine in your car, but the K24 is able to run lean at low revs and light throttle openings. If this is also true for the engine in your car, then yes, the O2 sensor might make a difference, but otherwise not. The MOT check is under conditions of soichiometry btw, so the O2 sensor is working properly in those conditions.
 
Gulp .. just got a price from my local supplier - £200 for the front sensor and £59 for the rear !

Now a search on ebay reveals £33 ???? for the front sensor and £116 for rear ??? Strange me thinks.
 
^ LOL very strange indeed

out of curiosity, what size are the tyres btw ?

and are they the same size as on your previous car ?

while I'm at it, if same size as previous, are the brands different from what you had before ?
 
freddofrog said:
^ LOL very strange indeed

out of curiosity, what size are the tyres btw ?

and are they the same size as on your previous car ?

while I'm at it, if same size as previous, are the brands different from what you had before ?
Hi freddo they are standard 195/60 15 same as before - economy ones. hankooks rear, Prime^2 front.

Now don't laugh, but my front sensor is off and at the moment soaking in lemon juice !

Its a Denso - so I think it may have been replaced in the past.

see http://www.hondacivicforum.co.uk/9-honda-civic-discussion/26725-cleaning-oxygen-lambda-sensor.html


It cost me £1 for three lemons !
 
flyerphil said:
Hi freddo they are standard 195/60 15 same as before - economy ones. hankooks rear, Prime^2 front.

Now don't laugh, but my front sensor is off and at the moment soaking in lemon juice !

Its a Denso - so I think it may have been replaced in the past.

see http://www.hondacivicforum.co.uk/9-honda-civic-discussion/26725-cleaning-oxygen-lambda-sensor.html


It cost me £1 for three lemons !
Now I am curious about the results. Let us know if you get better a better milleage.
If you decide to buy the sensors, go for NGK. Usually Hondas don't like other than Honda or NGK oxigen sensors!
 
skhell said:
Now I am curious about the results. Let us know if you get better a better milleage.
If you decide to buy the sensors, go for NGK. Usually Hondas don't like other than Honda or NGK oxigen sensors!
Interesting because it has a Denso at the moment.
 
Now all you need to do, is track down the previous car and see what O2 sensor that one had LOL
 
Hi, purely from reading other threads on the O2 sensors (and not from actual experience, so don't shoot me!) the original fitted part can be a Denso. Probably depends on the engine and year? Again from other threads, the 6th gen doesn't like 'cheap' O2 sensors, so stick with Honda, NGK or Denso...
 
Original is Denso, well for the Cat sensor anyway. These cars are very fussy and will only work with specific models, so dont just buy any off ebay or anywhere else, as it wont work.

Give VTECdirect a call as they can probably source you an OEM spec one for cheaper.
 
Thanks exec. The one I have is probably original then.

I put the original one back on the car, after a good soak in lemon juice (ciric acid) then rinse in white spirit and allow to dry. No problems. Started Ok and behaved as normal. I am now waiting untl the light comes on, and then put a measured amount of fuel in, drive till the light comes on again - see if there is any difference.

Simple experiment. They recommend replacing them at 100k. Many people on youtube have cleaned theirs with positive results. Well see.
 
Try cleaning the EGR. There are excellent instruction on hondakarma.com.

6,7 l /100 km (47 MPG) is possible in optimal circumstances (long journey @ 80-90 km/h) with a 2-litre automatic.
 
How did you get on after cleaning the sensor?
 
exec said:
How did you get on after cleaning the sensor?

Hi update on this.

After cleaning the sensor, I put in 10 L of fuel in (the light was on) and then drove till the light came on again. It covered 61 miles on the 10 litres giving an mpg of 27.7 - this was all urban driving, no long cruises.

So ... I don't think cleaning the O2 sensor did anything. To recap therefore, it does 34 mpg on an extended cruise, and 27 mpg urban.

This is much worse than my last one, which would do 40 mpg on a cruise and 34 mpg round town. Its interesting that the difference cruise to urban is about the same ie 6 or 7 mpg. There is also 6 mpg between the two cars - the difference being that the first one was a pre face lift 2000 model whereas the present one is a late 2002 model.

So I suppose I should try cleaning the EGR and plate next. Thanks Damien.

For me 27 mpg just isn't good enough. Its a great car otherwise, in magnetic blue - the best color in my opinion.
 
There are some 6th gen Accords that have two lambda sensors, others have only one. Do you know how many sensors your old car had?

The fuel consuption of mine is also bad, I guess I will try to clean the sensor as you did and see if it makes any difference. BTW, mine only have one lambda sensor.
 
I think mine has two sensors, not sure.

The front one that I cleaned did not seem too dirty.

From further research, it seems that the EGR and ports, does effect mpg, some say between 1 to 4 mpg difference. They all say that over 100k miles EGR components do get clogged. Likewise, O2 sensors are approaching end of life.

However - it seems that problems with EGR or O2 sensors either puts the engine light on and/or causes driveabilty issues - ie surging at high rpm, rough idle etc. Mine has no issues, it drives smoothly and the engine light is out. Its just the poor consumption that's a nuisance.

can anyone on here confirm, that after cleaning the EGR and plate, they got better fuel consumption ???
 
freddofrog said:
valve clearances can also make a difference, and spark plugs
I think my clearances do need doing. I did check them, and they seemed OK, but it does sound a little tapety when cold. maybe i didn't do it correctly.

Brian have you any idea how much difference it makes?

The plugs are fairly new.

Perhaps if I cleaned the plate and EGR, new O2 sensor and got the clearances adjusted correctly .... THEN perhaps I would see a difference?
 
flyerphil said:
Brian have you any idea how much difference it makes?
I wish I knew, but I don't :unsure:

I've checked some more on tyre type, apparently the A rating are only about 2 mpg better than the E rating. Your's are C rating btw.

I suppose it all adds up though, let's say 1 mpg each for

A. valve clearances
B. tyre brand
C. tyre pressure
D. EGR (not one on my car)
E. O2 sensor (but IMO it either works or it doesn't, but I'm open to refs that show age can make a difference to mpg)
F. carbon build up (IMO the biggest factor of the lot, and I reckon that cleaning additives in fuel can help this)

while we're at it, you could also add the MAF sensor into the mix (probably much more than the O2 sensor)

I do wonder why you sold the previous car though LOL
 
freddofrog said:
while we're at it, you could also add the MAF sensor into the mix (probably much more than the O2 sensor)
From memory the 6th gen uses a MAP sensor, not sure if these suffer the same issues that MAF sensors do?
 
Josh2109 said:
From memory the 6th gen uses a MAP sensor, not sure if these suffer the same issues that MAF sensors do?
if they do use MAP, I would agree that issues are less likely
 
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