Ian C Posted January 1, 2012 Share Posted January 1, 2012 What ho chaps, my Mondeo is giving me grief again. After finding out the battery was shot, I replaced it and thought everything would be fine. However, I'm now struggling to hit 29mpg around town driving like an angel, whereas it used to easily do 35mpg, and push for 40mpg on my work commute when driven carefully. I'm pretty sure this wasn't a problem a couple of hundred miles ago. I'm a pathological monitor of fuel economy as it is one of the first indicators of a problem, so I know exactly what I should be getting under what driving circumstances. Dropping from 38 to 28mpg without changing driving style isn't down to the cold weather! Here's the things I've checked/observed so far: Engine power output and delivery is normal, car is perfectly driveable, and starts nicely now with the new battery. No black smoke out the back under normal driving The rear calipers aren't binding because of the handbrake mech seizing (common problem with these) Tyres are correctly inflated Air filter is clean Oil is OK The MAF plug is plugged in OK No smell of diesel ever, no leaks around the fuel filter or injectors where I was monkeying when trying to diagnose the non-starting problem. I don't get it. I'm not using the aircon or the heated screens unduly, not that running those even permanently would drop 10mpg. If there was drivetrain drag it'd not coast properly and would feel sluggish. Binding brakes would stink and you'd feel the heat off the wheels, and even then it wouldn't cause 10mpg drop. Overfuelling would cause black smoke and probably quite noticeable changes to engine 'feel'. And it's not leaking diesel out. Where the hell is my fuel going?! The only change I made was swapping the battery. This has reset the ECU as it were, but that again shouldn't cause such a difference, especially after 150+ miles. Plus I'd feel it if it were chucking in 25% more fuel for the same load. -Ian Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 1, 2012 Share Posted January 1, 2012 not much help but my tdci focus is doing the same. does yours have cold starting problems? spoke to ford and they suggested bringing the car in for an ecu firmware update. mine is the 1.8 tdci engine and struggles to return 40 mpg on a decent run. Quote Link to comment Share on other sites More sharing options...
Scott Posted January 1, 2012 Share Posted January 1, 2012 Low MPG with trouble starting I think is generally down to the injectors on the modern engines, not so sure about the older ones. Quote Link to comment Share on other sites More sharing options...
jagman Posted January 1, 2012 Share Posted January 1, 2012 I think there have been injector issues with the mondeo, they need re adjustment at dealers on routine service ,this seldom happens once cars are of an age , leads to overfuelling and injector and cats failing Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 1, 2012 Share Posted January 1, 2012 have you tried any fuel system cleaner? Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 2, 2012 Author Share Posted January 2, 2012 It's starting perfectly, cold or hot, as mentioned in the list of things I've observed/tried In fact it's better than I've ever experienced with it, the glow plug light goes out quickly and it fires up on one or two turns rather than 4 or 5. It's the old TDDi engine, so it doesn't have a DPF or coded injectors or anything silly like that. I can't believe it needs fuel system cleaner run through it as the power deliver is perfectly normal, it hasn't changed, yet this low economy issue has reared up in the last couple of hundred miles, very suddenly. All I did was replace the battery with a new one Quote Link to comment Share on other sites More sharing options...
l.chris97 Posted January 3, 2012 Share Posted January 3, 2012 (edited) What year is it ian.....check the cluster for dtc's.......done my masters threw ford and its common on the 2002 - 2006 ( if its this model ) that when u have a flat battery or if u disconnect it u loose the Keep Alive Memory, radio code, long and short term fuel trims etc.....if there is no dtcs i'd suspect the ure pcm has defaulted to its factory programing and i do know for sure that the monty both di and dtci had updates for overfueling problems.....but i'd start with the dtc's mate same goes for the focus tubby so i'd take her in to the garage and check if ure pcm calibration is up to date Edited January 3, 2012 by l.chris97 (see edit history) Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 3, 2012 Share Posted January 3, 2012 your having better luck than me by the sound of it, mine now stuggles to start every single time. Garage time AGAIN by the looks of it. Quote Link to comment Share on other sites More sharing options...
Tyson Posted January 3, 2012 Share Posted January 3, 2012 Is it possible that when connecting the battey you might have frazzled something? Seems the only possible solution if the only difference is the battery. Quote Link to comment Share on other sites More sharing options...
Scott Posted January 3, 2012 Share Posted January 3, 2012 your having better luck than me by the sound of it, mine now stuggles to start every single time. Garage time AGAIN by the looks of it. Have you had a look at the EGR valve? This causes all manor of starting problems. I ended up blanking mine off last year as I was fed up with it. Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 3, 2012 Share Posted January 3, 2012 Not yet Scott, will have a poke around at the weekend and have a look then cheers. If it carries on I will just sell it and get something reliable. Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 17, 2012 Author Share Posted January 17, 2012 Just to report back on this, I realised on a long journey that the temperature gauge wasn't ever reaching halfway. If I sped up, it'd climb a little, and when I slowed back down, it dropped back to the coldest value. As it's always taken an aeon to warm up I hadn't had the chance to notice this doing short runs at low speeds around the city in the cold - this was "normal" behaviour. So, an engine almost permanently on the cold start cycle - that'd use up a fair bit of fuel wouldn't it? So I check the mondeo forums and it appears the oil cooler thermostat is the no1 culprit for this behaviour. After a period of bad weather and feeling under the weather, I finally get to swap the bit out today. The old 'stat was jammed open, that's a good sign, thinks I, and Lo & behold, I'm back up to 38mpg on a 7 mile trip through the city to work tonight Bonus, the car was kicking out warm air from the vents after a mile instead of the usual 7! Yay warm air when driving to work in the winter, result! So it's probably always had this problem and just gradually got worse to what I saw recently. I also took the oppo to clean out the sludged up intake runners and manifold, holy smoke they were like furred arteries blummin' diesels. -Ian Quote Link to comment Share on other sites More sharing options...
Scott Posted January 17, 2012 Share Posted January 17, 2012 Just to report back on this, I realised on a long journey that the temperature gauge wasn't ever reaching halfway. If I sped up, it'd climb a little, and when I slowed back down, it dropped back to the coldest value. As it's always taken an aeon to warm up I hadn't had the chance to notice this doing short runs at low speeds around the city in the cold - this was "normal" behaviour. So, an engine almost permanently on the cold start cycle - that'd use up a fair bit of fuel wouldn't it? So I check the mondeo forums and it appears the oil cooler thermostat is the no1 culprit for this behaviour. After a period of bad weather and feeling under the weather, I finally get to swap the bit out today. The old 'stat was jammed open, that's a good sign, thinks I, and Lo & behold, I'm back up to 38mpg on a 7 mile trip through the city to work tonight Bonus, the car was kicking out warm air from the vents after a mile instead of the usual 7! Yay warm air when driving to work in the winter, result! So it's probably always had this problem and just gradually got worse to what I saw recently. I also took the oppo to clean out the sludged up intake runners and manifold, holy smoke they were like furred arteries blummin' diesels. -Ian Good result, not a lot of money involved Just about everything that has flow going through it ends up in one hell of a nick with the old oil burners. The EGR valves cause nothing but bother IMO, hate the things. Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 30, 2012 Share Posted January 30, 2012 Thats quite intersting, my focus doesnt kick out much heat at all until im almost at work so prob a good 5-6 mile drive... Will get the garage to investigate. Also have developed a nice whine when the turbo kicks in an no boost at all, the turbo is spinning up, but none of the bosot is getting to the engine. great. Quote Link to comment Share on other sites More sharing options...
Thorin Posted January 30, 2012 Share Posted January 30, 2012 I recommend selling it and buying a Ford Puma, much more fun and I get 40mpg Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 30, 2012 Share Posted January 30, 2012 Its the wifes car really, she is looking to sell it and get a megane with the bum shape boot..... Would rather a broken focus TBH! Quote Link to comment Share on other sites More sharing options...
Scott Posted January 30, 2012 Share Posted January 30, 2012 Its the wifes car really, she is looking to sell it and get a megane with the bum shape boot..... Would rather a broken focus TBH! You seriously need to talk her out of that one, you will get nothing but bother IMO. Quote Link to comment Share on other sites More sharing options...
TubbyTwo Posted January 30, 2012 Share Posted January 30, 2012 Oh im working on it dont worry! Quote Link to comment Share on other sites More sharing options...
Guest kaiden Posted February 24, 2012 Share Posted February 24, 2012 How about taking the injectors out, and taking them to have their spray spread and pressure tested? Some diesel specialists will old charge you if they find something wrong with an injector and it needs cleaning/resetting... Just a thought! (although I would suspect some sort of smoke, as dirty injectors usually results in un-burnt fuel, I think? Quote Link to comment Share on other sites More sharing options...
Ian C Posted February 25, 2012 Author Share Posted February 25, 2012 Thank you, but I wrote up the fix in post #12 Oil thermostat. Quote Link to comment Share on other sites More sharing options...
Guest busta200 Posted February 28, 2012 Share Posted February 28, 2012 cant believe a oil thermostat would cause so much difference in economy. makes me wonder about by focus now as never seems to warm up Quote Link to comment Share on other sites More sharing options...
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