Very low MPG mystery..

[thesoundone]

Hi everyone,

I just recently bought a 2.0 TDI 140 Sport Altea on a 55 plate. It's the BKD engine.

Soon after I bought it I realised something was amiss as the best I can manage out of it is about 38mpg average on the trip computer. If I tootle along at 50 I can get the short trip computer to stretch to 48mpg. As soon as I go over 60 it's plummets down below 40mpg.

I've Manually calculated the MPG over a couple of full tanks and I'm getting 41mpg over mostly motorway miles at between 60 and 70mph and some short trips down the A1 and into town. Seem to be getting around 450 miles to a tank.

Things I've noticed on the engine include a slight/faint 'wooooooo' kind of sound from the turbo at low rpm's. A sucking air/hiss sound after gear changes and a pretty loud turbo whistle/hiss whilst on boost. (A lot more than our skoda fabia 1.9 which is a thin whistle on boost). Sometimes at idle it starts to hesitate a bit and then regains normal idle after a while. Sometimes when coming off the power at speed, it seems to shake slightly.

It seems to have a fairly flat power curve in the midrange to me compared to our skoda which is very rapid indeed. It's doesn't start too well when hot but I think that's probably the starter motor. Overall the engine sounds really tight and quiet and feel pretty smooth in general.

Carbs completely standard to my knowledge.

Things I've done so far are:

1) Air filter
2) Fuel filter
3) New Bosch MAF
4) Turbo clean using Mr muscle in the exhaust side.
5) New EGR valve (replaced by dealer before purchase)
6) Checked inlet manifold for clogging and wasn't too bad at all, just a bit oily.
7) 2 lots of injector cleaner through the tank and some hard driving to try and clear it out a bit.
8) Checked intercooler hoses going in and out which seem to be ok apart from some oil around the clips. Sprayed some soapy water here and no apparent air leaks)
9) It's had a full diagnostic at a local place and boost pressure is good and all temp sensors working within spec. No fault codes at all.
10) New battery
11) Oil and filter (done by the dealer)
12) timing belt and water pump (done by the dealer)

I'm completely stumped! Is this really all I can hope for in terms of MPG? Our skoda returns 60 average so really disappointed at the minute.

Does anyone have any suggestions or anything I might have missed? It's a real head scratcher..

Thanks if you didn't get bored and read all of that lol! Really appreciate any replies.

Cheers

 

[PHILMEWAGON]

does the car have a DPF?

I only ask because mine has recently regenerated and my car now does an additional 70 miles on a tank of fuel. That's a big difference.

Prior to regeneration the car felt lumpy and sluggish.

Im sure there are lots of possible reasons, and even if you have a DPF it may be nothing to do with this - im just offering up possibilities.

edit: do you know what the expected MPG is for the vehicle?

 

[thesoundone]

Thanks for the reply,

No it doesn't have a DPF. I did wonder at one point whether there might be a blockage in the cat though..

To be completely honest I haven't checked what the expected mpg should be but after owning around 5 TDI's I expected it would the same as the others.. I could be wrong though. I'll check.

Cheers

 

[iain1970]

Imdoma 20 mile each way commute to work over b roads, 50mph a road and 30mph urban routes. I get 55 mpg going and 45mpg back (traffic). I get 450 miles out of a tank and have had the ghost train sound for the four years I've had my TDI Sport. All sounds perfectly normal to me.

 

[Mao]

I have the same engine in mine, but remapped and I get about 420 a tank. I'm either driving around town or a good speed on the motorway. If I pootle on A roads i can manage 50 mpg at an absolute push.

 

[SNAP-ON]

I have same vehicle on a 54 plate with only 55k on the clock . I get the same slight judder/missfire on idle at times but intermitten . Some times u feel the whole car judder other times just slightly . Ive read this is normal bkd behavior . My midrange is also a bit flat but again these engines dont seem to be as agressive as the 1.9tdis . Ive driven lots of 1.9tdis and i know what you mean as in the power is an instant punch and they seem to fly compared to the bkd . I get around 450 to a tank also . The hot start issue will prob be due to old starter motor . Ive scanned mine an have the usual cylinder one glow plug wiring electrical fault which will prob require a new injector loom and hopefully sort the judder issue when i get round to sorting it .
Remember though that just because there is no fault code there could still be an issue but this needs live data to be looked at etc as a temp sensor could be graphing wrong when looked at live !
Ive also done the same ie new oem filters and oil but still running oem maf from day one lol

 

[SNAP-ON]

Forgot to mention i had mine remapped in october and much better power wise , ive never seen a traction light flash so much even in the dry lol . I can get 56mpg on motorway sitting just under 70 and around town stop/start 38-42 mpg but average around 45-50 most of the time .
Ive also found that using shell normal diesel i get the most mileage . If i stick £20 in these are my findings - tesco diesel just under 100 miles , esso diesel around 120 miles and shell diesel around 145 miles !

 

[Mao]

Christ, I'm going to try shell! Mines also a 54 plate.

 

[SNAP-ON]

Try it lol . I do 100miles a week exactly the same route etc and although shell is a couple of pence a litre more it seems to be well worth it . Ive done this test a few times and everytime shell wins .

 

[Mao]

I will do You seem to have solved the problem here

​

The soundone- have you checked you tyre pressures? Maybe they're running on the low side?

 

[thesoundone]

Thanks for the replies!

I've checked on the official expected MPG for the 2.0 TDI sport and its showing a combined of 47.9 which over 55 litres should be about 570 miles! Mine is returning 450 miles which in the real world (not on the computer) is 37mpg. On the computer my long term average sits at 38mpg and the current trip sits at about 36-37mpg if I'm doing 70mph on a long run or can be 45mpg if I cruise at 55mph on a long run, sometimes if there's enough downhills it will hit 48mpg. I've never hit 50mpg in this car yet.

To me that doesn't seem right and seems to be below what should be expected but based on what you guys have said I seem to be getting the same tank range so I might just let it be. Incidentally, my tyre pressures are pumped up to full load specs but my tyres are all different and I got informed the other day that one of them is a winter tyre. Could that affect mpg?

 

[thesoundone]

Ive scanned mine an have the usual cylinder one glow plug wiring electrical fault which will prob require a new injector loom and hopefully sort the judder issue when i get round to sorting it .

Yep, I wondered about this loom also. I'm tempted to change it at some point as its not a massive job by the looks of it.

 

[Alibaly]

Interesting to hear that others also have the whooo noise when changing up in the lower gears. I have a 59 plate 2.0 tdi also and long term trip mpg shows 46.9 and when measured from full tank to full tank varies between 42 to 48 which is much the same as i previously managed with my golf plus 1.9 tdi (105) over 7 years of mixed driving.

 

[thesoundone]

Interesting to hear that others also have the whooo noise when changing up in the lower gears. I have a 59 plate 2.0 tdi also and long term trip mpg shows 46.9 and when measured from full tank to full tank varies between 42 to 48 which is much the same as i previously managed with my golf plus 1.9 tdi (105) over 7 years of mixed driving.

I think, but I'm not 100% sure that you're car has the common rail engine. I had an 09 2.0 Golf which had that engine it was great. Much more refined than the earlier ones. I used to get 50mpg average in that car and I could get 650 miles to a tank.

 

[How-J]

Mine "woo's" too, although performance not affected.
We've had the car (a 2.0tdi sport) for 60k miles now and its never got near 50mpg unless coasting downhill.
One thing that made a big difference was when the rear brakes had to be replaced due to seized calipers. Clearly been binding for a while as at the time we were lucky to get 40mpg.
On a day to day basis, crawling through town and onto open roads; we get around 35-40 if gentle with the throttle. On a run sticking to 70 we'll get 43-45.
The 2.0 does have a narrower power band to the 1.9, so maybe you notice that more than anything?
I never use supermarket fuels as I've found it to be a false economy.

 

[thesoundone]

Mine "woo's" too, although performance not affected.
We've had the car (a 2.0tdi sport) for 60k miles now and its never got near 50mpg unless coasting downhill.
One thing that made a big difference was when the rear brakes had to be replaced due to seized calipers. Clearly been binding for a while as at the time we were lucky to get 40mpg.
On a day to day basis, crawling through town and onto open roads; we get around 35-40 if gentle with the throttle. On a run sticking to 70 we'll get 43-45.
The 2.0 does have a narrower power band to the 1.9, so maybe you notice that more than anything?
I never use supermarket fuels as I've found it to be a false economy.

Well isn't that funny.. I've got the day off so I went outside and jacked the car up earlier and the drivers side rear caliper is sticking. I could barely turn the wheel. Went for a drive to my local garage to tell them and when I got there the wheel in question was red hot. They had the wheel off while I was there and greased the calipers and had a visual check. Took it out for a spin and seemed fixed. however, I just got back and the wheel was hot again. Must be an intermittent thing. Did you get the brake lines to the calipers changed as well? Looks like I'm going to have to get it all replaced. Could be the reason for low mpg though..

Also, the front wheels don't do a full turn when spun but the garage says tha'ts the transmission dragging. Is that right?

 

[How-J]

We had calipers and discs replaced, as they were very corroded and don't get used that often as the car is often run with not much load in it.
Common issue on most cars with rear discs. Our other cars have rear drums.

 

[robint]

My rear discs were dragging due to a seized caliper (9 years old though) - it's all easy to get at and parts are relatively cheap as the same as many VAG vehicles. Could certainly affect mpg!

 

[SNAP-ON]

Yes front wheels dont spin freely due to trans drag like garage said , its almost like front brakes are binding lol .
Oh and tonight i done a 15 mile trip doing 30mph in 6th gear and was getting 62mpg on computer lol i even took a pic !

 

[CrispDust]

Off topic but I've noticed im getting 2-4 mpg better since I changed both drive shafts a month ago....