Poor MPG and fault codes.

[tony19]

Hi all

I just got a Audi A6 2009 2.0 TDIe 136bhp Multitronic and the fuel consumption is very bad.
The best i can get out of it is 35mpg and thats being very gentle on the pedal and not going over 70mph on motorways.
Car was serviced 3000 miles ago.
I did a scan today and the only fault that came up is P0674 Glow plug cylinder 4 electrical fault. Permanent.
Appart from that nothing else came up.
Any suggestions on the consumption and why the glow plug fault came up.

thanks in advance

[Rob69]

Get it hooked up to a decent diagnostic tool or vcds, check engine is actually getting up to full operating temperature ( despite what the dash gauge says) , check MAF sensor readings (required and actual) to see if MAF sensor has degraded, check air filter cleanliness, DPF soot loading, not sure what you can check injector wise on the CR engine via diagnostics? has it had the ' software upgrade' done ? check brakes for drag, tyres for under inflation, wheel misalignment etc.
Not sure what MPG you are hoping for, maybe 40 'ish ? the A6 is a bigger car ( 2 tonnes 'ish?)

[tony19]

Thanks for reply Rob.
Air filter was changed last week, Brakes checked for drag, tyres air pressure checked and MAf readings are on the image below.
The DPF soot loading and injector wise have not checked it yet.
Car did not have software upgrade as what i have been reading is that a lot of people are not happy with it.
I was hoping to get it 40ish MPG combined with a very carefull driving, inc motorways.
This model supposed the most economical..

Does the Glow Plug fault has any affect?
33020

[Rob69]

Glow plug would have no effect on long term mpg, does it keep coming back once cleared? the MAF reading you show doesn't mean much without other data, you need to compare what the ECU is expecting to what the MAF is measuring, I see your engine temp is only33'C, presumably that is just after start up!

[tony19]

The glow plug did not come up anymore after clearing. After 40 miles the coolant temp was constant at 80 (see image) but on dash it shows just over 90.
The other thing to mention is that if i put my foot down the car doesnt really go anywere, just picks up speed slowly and constant.
I know is only 136bhp but should have bit more of a kick once i put the pedal right to the floor..
My wifes A4 Avant 130bhp would leave mine miles back,,,

33021

[Rob69]

See if you can get some better MAF sensor checks done. I've had a MAF sensor fail and it sort of creeps up on you gradually, then you realise how bad it had got once you fit the new one. Temp at 80 is a bit low also, but not sure if that would have major impact on the mpg, does it drop when driving slowly round town or coasting down a long hill. I changed my stat in my old passat in january as it was hanging round the mid 70's and low 80's while driving, a new stat saw it sitting in low 90's on a run and quickly coming up to high 80's from a cold start, but mines the old PD engine.

[zollaf]

i think 80 degress explains a lot. funnily enough i was testing an overheating passat pd and with the ecu reading 89 degrees, the gauge reads 90. at 117 degrees, the gauge still reads 90,. only when the ecu hits 119 does the gauge actually move, straight to 120.

[Rob69]

The dash gauge is only there to give folks something interesting to look at, might as well be painted on !!

[tony19]

Update:
Had the car checked with VCDS today but the Measuring Blocks were disabled.
The only way to check the car was to go through basic settings and Advanced Measuring Blocks where i had to hold down the brake and throttle pedal and the system does checks to the car by itself for a few minutes.
Everything came up fine, no issues.
So i could not measure Air mass sensor what ecu expect and what is measuring...
Was reading on Internet that vag cars after 2009-10 you cant get to Measuring Blocks..
DPF was fine.
Another thing to mention is that while the car is on,inside the cabin it sounds as the engine fan is on, but its not.
It has been like that since i bought it and i thought is just the type of the engine..
I done a 50mile trip today mostly on motorway, not going over 70mph and barely got 38mpg :zx11:.
Driving in town that would easily drop to 30mpg.
Anymore suggestions plz ?

[dan2485]

what tyres are you using as this has a big impact on the MPG.

what sort of rev range are you using?

[tony19]

Car has genuine Audi 18" wheels with all 4 almost new tyres Champiro UHP1 245/40/zr18 97w xl. Tyre pressure is correct.
Car came with these tyres.
As the car is auto the gears usually change around 2000revs or lower.

[dan2485]

Those tyres are F rated for fuel ecomony, have you had a higher MPG achevied before.

If yes but in the summer that will be due to the Higher air pressure.

[tony19]

Hi.
I just got the car two weeks ago..

[dan2485]

I have a TDIe with a manual gearbox and can achive around 50mpg in winter on the motorways which increases to around 70mpg in the summer due to the higher air pressure.

you could have as indicated before a MAF issue, but tyres do make a big differance.

Your tyres are B rated for grip which impacts on the fuel economy.

I had pirellis on mine at first and they would wear out very quickly but the grip was good. I now have goodyears for the noise and fuel economy but i have 17 inch wheels.

[Rob69]

When you rev the engine does the 'fan on' noise rise in line with engine or stay the same? just wondering if you have a restricted dpf, does it ever do a regen?
I have a newish Up! and you have to open up each measuring block individually in vcds, bit of a chew on tbh.

[dan2485]

look at this post did 3 years ago it tells what look at in the advanced measuring blocks.

DPF pressure sensor or just a blocked DPF (http://www.vwaudiforum.co.uk/forum/showthread.php/154455-DPF-pressure-sensor-or-just-a-blocked-DPF)

[tony19]

The "fan on" noise raises in line with the revs.
as i had the car for onnly two weeks i am not sure if it had a regen., but two days ago i done around 20 miles to get to work and when i turned off the car the fan stayed on.
waited in the car for 5min and the fan was still on.
Coudnt wait anymore to see how long it will take so i left for work.
I thought that was the regen.. but there was no lights at all on dash.

when we checked car with vcds the guy said the DPF is fine, cant remember excatly the figures but was smth like zero point smth % and i think 14gr of soot level.
It showed last time when the regen was done but it showed smth like 123265km :confused:. car has 105.000 miles.

[Rob69]

Could the 'fan on' noise be the turbo? just wondering if the VNT actuator is playing up, which I've read can be a failure on these CR engines. If not that then I'm thinking DPF blockage but your soot levels look ok (not that I'm a dpf expert btw!) the mileage since last regen looks way out though - last regen at 123265km = 76424 miles. Saying that though the fan running on when parked does indicate a regen underway. Sorry can't offer much more advice as I'm not familiar with these engines or dpf. The VCDS guy should have run and saved a log for you, then you'd have all the figures.

[tony19]

When i got the car Vcds the guy done a update on the dash so now i got oil temp and boost graph. (See image)
the boost on the dash never passes the 75% no matter how much i push the car. I put foot to the floor and it did not make it past 3/4 so it could be actually the turbo or VNT Actuator..
Anyone else has the same display with Boost, and does it go to Max if you floor it?
Thanks for the help so far

[tony19]

Used a Wynn turbo cleaner today aerosol but has made no difference.

Had the fuel light come on today and done calculations from last time i filled up and result was 31mpg :zx11:

[zollaf]

tony, you have said the car is only running at 80 degrees. i have already said this will have quite an impact on the mpg, why dont you listen and go fit a new thermostat ..

[Rob69]

Don't rely on the accuracy of that dash boost 'gauge' too much, mainly a trinket to keep you amused! If you're only getting to 80'C it will impact your mpg. I clawed back some mpg earlier this year on my old PD passat by fitting a new stat, it now comes quickly up to 90'C (VCDS reading not the dash gauge) whereas before it was mid 70'S and crept up to mid 80's if working hard even though the dash was reading 90'C all along. Strange thing is the old stat tested ok in a pan of water with a thermometer.

[niall campbell]

could be the Coolant Temp Sender is faulty rather than the thermostat

I think the fuel temp sender is the same as the coolant ........................ so you could swap them over to see

You could also just disconnect the CTS ...................... the car will default to cold weather start ................... more diesel but more power

[tony19]

Update:
I changed the Thermostat, Air flow meter and cleaned EGR with no difference.
Probably i will change the coolant temp sensor too at some point this week.
Yesterday i got my car remapped by Advanced Tunning dealer Te in Essex.
we done Dyno runs before and after and the car still had 134bhp.
After remap we done a few more Dyno runs and the car has 183bhp now which i am very happy. And you can really feel the difference while driving.
As i left from there i done 70miles motorway only to get home and drove between 70-80mph and got the average of 48mpg.
I know is still below of what these cars should get on motorway only, but im happy with it.
I will update again if i see any changes or find anything..

[dan2485]

What was the point of asking for help when you were getting the car remapped?

[tony19]

I did not plan to get it remapped.

[niall campbell]

At 70 to 80 mph , I would expect 45 to 55 mpg

60mpg is around 60 mph

[MarkTM]

I think any decent remapper wouldn't remap a car that wasn't 100% to start with...as it will only emphasis/worsen them

You mention you have the multitronic (sometimes call multichronic by many on here due to problems)?

With 105k miles the tranny fluid/filter should have been changed twice at 38k miles...so not that far off it's third. But I am guessing that won't have happened as most don't bother. VCDS won't identify any transmission issues btw.

So with the remap I would say enjoy the extra power until your transmission fails :(

[tony19]

The transmission fluid i dont think it has been changed and i have in plan to change it soon.
hopefully in the next two weeks.
I just got back feom European trip and done 3100 miles in 10 days with the car.
95% of the journey it has been done on motorway between 70-80mph.
The average i got from on board computer is 45.5mpg but with my calculations from the tank I averaged 41 mpg.
Motorway only surely should have been close to 50mpg..:(

[niall campbell]

do you know how to reset the computer ??

At 70mph you should get 50 mpg at a push , any faster & I don't get 50 mpg with my manual car

I change gear when I am near 3.000 rpm and aim to have at least 2,000 rpm when I change gear.

[muller1]

Hi all

I just got a Audi A6 2009 2.0 TDIe 136bhp Multitronic and the fuel consumption is very bad.
The best i can get out of it is 35mpg and thats being very gentle on the pedal and not going over 70mph on motorways.
Car was serviced 3000 miles ago.
I did a scan today and the only fault that came up is P0674 Glow plug cylinder 4 electrical fault. Permanent.
Appart from that nothing else came up.
Any suggestions on the consumption and why the glow plug fault came up.

thanks in advanceI had a poor fuel return on my 2009 Q5 2 ltr Tdi and the tail of the car was getting black.
I contacted Audi and would have needed a mortgage to pay for their services and a new set of Piazza crystal injectors.
I spoke with Diesel Bob at Ribble Valley Diesels on 01254 878353 and I ended going down from Aberdeen to have him work his magic.
He replaced all the injectors because it is not possible to service them.
Audi wanted over £500 each plus fitting, plus, plus, plus then Vat they estimated round about £3000.
I got all that done, plus a new rocker cover with the troublesome breather replaced and anything else it needed for round about £1700
inc vat.
Bob is the greatest with diesels and I have used him for my business previously and he is the only guy worth going to.
I can get between 35 mpg and sometimes hit 55 mpg depending on how I drive.
If you speak to Bob just say Mike Muller says he was asking after him.

Regards.
Mike