Jump to content
Sign in to follow this  
Guest plesbit

Increased fuel consumption

Recommended Posts

Guest

Sorry this is car not boat but I thought it might be useful to tap into the expertise here!

Our car was given its third annual service earlier this month and ever since it has used about 20% more fuel than before. The range has been reduced from 450-500 miles per tank to about 390 or so and the on board fuel computer is recording consumption figures of 37-40mpg at 65-70mph on a level road instead of the previous 46-50mpg.

Having been away at the weekend, and only just discovered the problem, I have not yet had the opportunity to speak to the dealership where the vehicle was serviced. However I did get a chance to speak to the dealership from which it was purchased. According to them the car would not have been faced with any kind of electrical tampering during what is effectively the 36,000 mile service (though it has actually only done 29,000 miles) as it is merely a change of oil, plugs and every filter under the sun.

So what could they have done to bugger up the fuel economy? The engine management system is not showing any errors, the engine sounds and behaves fairly normally in other respects. Naturally I will be taking it back to the dealership but I am expecting a whole lot of time wasting as they do everything to shrug their shoulders. My only thought was perhaps a problem with breathing (wrong / duff air filter) but someone at work has suggested the wrong grade engine oil and wrong sparkplugs might also have this effect. Any other ideas?

Share this post


Link to post
Share on other sites

Outside air temperature and humidity can contribute to this.

The Colder and higher the humidity the more BHP the engine produces.

I take it that's yours is a petrol engine ?

There's a high chance they gave the ECU a reset when they plugged in the Computer.

Everything would be back to Learn mode, so all the MPG from the computer will be the factory set ones unit it learns your driving style etc etc.

Share this post


Link to post
Share on other sites
Guest

Unfortunately I think I am going to get a lot of this at the garage as well. It's not a variation in conditions like that. For three years, through spring summer autumn and winter it hasn't varied a jot. Then suddenly in three weeks from the service it has changed considerably. Something has changed - and it's not the ECU as it wouldn't have been plugged in.

Share this post


Link to post
Share on other sites

Have you carried out a analogue test ? Fill the tank up and count the millage ?

My trip computer on the Nissan is always biased, it tells me it does 26mpg but when i do the analogue test its only doing 22mpg

and that's over a average of 3 tank fulls.

Share this post


Link to post
Share on other sites
Guest

Yep. Normal range of the tank driving to and from Great Yarmouth to work 5 days a week is 450-470 miles. On the open road it'll do over 500. So setting off from Salhouse to do the 150 mile to Ashford journey should not have been a problem. Imagine my surprise then when we had run out of fuel by Thurrock. That was what first alerted me to a potential problem and caused me to turn on the fuel computer. I have regularly used this to trip motorway journeys so I know what readings to expect and it immediately confirmed my suspicions showing much lower figures than usual. Our return trip last night underlined these findings from Friday.

Share this post


Link to post
Share on other sites

mmm i would get this down in writing Simon, as its the kind of thing they will sweep under the carpet unless you hit them with Hard facts from the start.

As your 1st post required a few questions until the full picture became apparent that you had already have compared the different options of calculating the MPG :)

Share this post


Link to post
Share on other sites
Guest

Yes I expect that will be the case Brian. I am sure the garage will do everything they can to put it down to my imagination or come up with pseudo-plausible explanations to avoid having to do anything. However since I will be standing right there it will be a fairly quick process to dismiss them. But rather than just dismiss what it is not, I'd also like to be able to suggest one or two things that it might be.

The reason my post was so short was because I hoped people would just accept my word that there was a problem and come up with some possible causes! ;)

Share this post


Link to post
Share on other sites

Sorry Simon i thought it was more advantages to put my foot in the Garage Shoes ;)

I still cant understand how MPG can differ so much though, if i would have had any more ideas id add them.

Ill put a bet on the Cat though.

Then again could be a dirty Maff sensor, causing the ECU to Over fuel slightly.

The only way to find out is take it to Clives, as we will be able to monitor Every Sensor and fuel emissions.

Share this post


Link to post
Share on other sites
Guest

Dirty sensors or cat related problems I would expect to build up over time. This happened all of a sudden.

Share this post


Link to post
Share on other sites
Dirty sensors or cat related problems I would expect to build up over time. This happened all of a sudden.

Dosent work like that :(

Share this post


Link to post
Share on other sites
Guest
What car and what engine is it Simon.

It's a Ford Mondeo (you've seen it!) ;) . The engine is a Duratech 1.8 HE petrol.

Off to the dealership now. My BS radar is already on high alert. Isn't it lucky my employer barely registers whether I am at work or not - all this pissing around I've had over the last few weeks with cars would have been a much bigger problem if I was chained to a desk rigidly from 9-5pm.

Share this post


Link to post
Share on other sites

Oh yes I remember, you sure some wag hasn't set the computer to read in U.S. MPG I did it on our hearse G.T. to see what would happen and got a similar result. Except for the having to fill up earlier bit that is. :-D

Share this post


Link to post
Share on other sites

Simon,

You do prety well on fuel consumption mine is a 2 litre mondeo and has never seen better than 40 mpg, then again don't think it has seen 70mph either on the motorway.

Secondly what Brian says about the sensors makes a lot of sense, these control the fuel flow via the CPU and can and do go down overnight so if it has decided to play up it could well be chucking in a load of extra fuel, would certainly think the air filter is worth a look but it seems a huge difference to be just that bearing in mind it is a new filter, unless the technician (young trainee mechanic) has left his sandwich's in there. Plug gaps would also have a detrimental effect but again they would have to be so far out to cause that much difference that I would think there would be other signs.

Have found that ignoring service intervals and only fixing it if there is something broken is a good idea on modern cars. Had mine from new, it has 180,000 miles on the clock now and has only ever had 5 services, always insisted on fully synthetic oil and changed it every 30,000 miles. So far it has had a clutch, rear axel bushes, 4 sets of brakes 1 set of discs, not bad for 7 years.

Previous Mondeo had regular services and loads go wrong with it to the point that I decided never to look at a ford again, was only because the new model seemed so much better than anything else in budget that I took the risk.

Ian

Share this post


Link to post
Share on other sites

Hi Simon

This is a drastic reduction in fuel economy, If you are confident with the manual checks you have carried out on this consumption and it has definitely only occurred since the service, I am sure that they will find something conclusive.

I have experienced new air filters being replaced and sections of the plastic packaging being left on the surface, even Air Mass sensors being damaged during the replacement of said filters. Wrong plug gaps if replaced can have an effect. The most common thing I have seen is handbrakes being over adjusted just enough to add resistance.

It is also possible that a pipe or hose has not been fitted correctly during the replacement of the air filter or a pipe being knocked of dring the service and air leaks giving incorrect air mass readings to the engine management systems, thus, over fuelling.

With the mileage covered I would find it highly unlikely if it is a blocked exhaust or cat.

But never rule out coincidental component failure. Very complex systems these days.

Share this post


Link to post
Share on other sites

One other point to raise with the dealership is if it had any recall or service measures carried out to the software of the engine management system.

A further point! Is it manual or automatic?

If an auto and the filter has been replaced in the box as part of the service it is possible oil level is down causing slight slippage.

Share this post


Link to post
Share on other sites
Guest

Hi all, thanks for the responses. I accept that computer components can fail and that co-incidences can happen. I paid the garage a visit this afternoon and they are going to take it in and check the elements replaced during the service. If it needs any work beyond that, like plugging into any diagnostic kit, then it becomes chargable which I guess is hard to argue.

By the end of the 30 days of November the (two) cars will have cost me over £1000 in maintenance alone. That's assuming this new problem with the Mondeo is rectified at no further cost otherwise it'll continue on upwards, annual road tax due next month as well.

And I thought the damn boat was expensive.

angry1.giftwo gunsangry1.giftwo gunsangry1.giftwo gunsangry1.giftwo gunsangry1.gif

Share this post


Link to post
Share on other sites

Get yerself a hearse G.T. Simon, 130mph, 2 services and 2 tyres in 42 months from new, total cost about £1200 and 45mpg and close to 1900 litres of room in the back for your boaty kit. :dance:dance

Share this post


Link to post
Share on other sites
Guest

Just to re-visit this thread:

I haven't actually checked the brakes, to be honest, but the car rolls freely and the smell of hot brakes is quite distinctive so I hadn't given it too much thought. It's always something else to look at though. It is manual and no, it has never been plugged into any diagnostic kit, from new, so far as I know, unless any of the first two services require that to be done. Other than the annual service carried out as per warranty requirements and a replacement sat nav system which was malfunctioning the car has never had any work done on it.

Ian, I am not a fast driver - I drive for economy and always have. You'd be surprised how much effect the tiniest foot wiggle can have. If plugs and air filter is all the garage is going to do then I am seriously tempted just to replace them myself but a part of me objects to that on principal. However I do don't doubt for a moment that no matter what they find when they get the car in they won't admit it could possibly have been anything to do with them.

Had a look at the latest Mondeo whilst I was in the dealership. Very, very nice car.

Share this post


Link to post
Share on other sites

May be worth while finding a good local fuel injection specialist to have a look.

only reason I say this is I once had an Opal Manta GTE that developed a slight miss fire below 1500 rpm , was due a service so booked it in to the local main Vauxhall agent thinking that the service would clear it. When it returned the miss fire was worse and occuring upto 2500 rpm so I took it back. They denied it was anything to do with them but said they would have it in and check, when it returned this time it was miss firing upto 4000 rpm and was virtually undrivable. Their suggestion was to change the engine managment CPU at a cost of £450, a lot in those days and when questioned they admited that they didn't know if this would cure the problem. When I really pressed the service manager gave me the name of a local fuel injection man. It cost me £45 for him to put right everything Vauxhall had put wrong and the car ran like a dream.

If they have altered any setting at all then it will send the wrong information back to the engine managment system, which will apply compensations that are not needed and could result in excess fuel being thrown in.

Ian

Share this post


Link to post
Share on other sites
Guest

To be honest I thought you were joking but a quick Google tells me otherwise.

The Mondeo owners forum appears to be something of a desert, which isn't surprising really because I guess the sort of people who buy Mondeo's are not really the sort who care enough about cars to spend their whole time talking to others about what it's like to own one. There are three technical questions in the Norfolk / Suffolk forum there, all without any sort of answer or even acknowledgement. Still, it was worth a look so thanks for the suggestion.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

×

Important Information

For details of our Guidelines, please take a look at the Terms of Use here.