Help Please 2.0 tdi 140 - Poor fuel consumption & low coolant temp

mladen

Registered User
I've had my used 2010 Audi A4 2.0 tdi for almost a year now and noted fuel consumption doesn't appear to be that great at all. Just had a 350 mile return from a full tank, if I do mostly long distance motorway I can squeeze 500 miles out of it. This just doesn't seem right?

I remember my old T-Reg 1.9tdi Audi A4 Avant pushing 800 miles on a long road trip, perhaps 600 miles if ragged it about town. I'd have thought with a more modern engine things would have been more efficient.

The car I have has the CAGA engine code and has had the emissions update by the previous owner, car now covered 150k miles.

The engine coolant temperature takes a good 20 minutes driving to get to 70 degrees, but then rarely passes it. The only fault code from a scan appears to be a faulty Glow Plug No 1, but this shouldn't affect fuel and temp surely?

Previous issues have included an erratic idle (see youtube video), but a new fuel pressure regulator sorted this. Having said that, there is still a bit of very minor idle vibration at times which goes when I give a bit of throttle. Also steering wheel seems to vibrate at times around the 70 mph mark (wheel alignment and balancing hasn't resolved the issue), no vibration at lower speeds. Car is on original clutch/flywheel as far as I'm aware., although no noticeable slip on clutch yet, but flywheel could be suspect?

Seems like a multitude of issues, although engine seems to run fine otherwise. If anyone has any experience in the above issues or could provide any pointers it would be much appreciated.
 

777GE90

Registered User
Does your temperature eventually hit 90? My understanding is that it is quite common for these Audi's to take a good while to warm up, you see lots of people reporting it, including mine too, the temperature seems to jump up and down below 90 for a good 20-30 mins of local driving (or at least 10 mins of motorway driving) before reaching 90.

However, it usually does warm up to 90 eventually and I can get 60 MPG on motorway journeys if I don't push too hard.

If you have the same size fuel tank as me, you are probably getting around 36 MPG which does seem low to me. I get 40 MPG if I am hammering it all the way.

I have a 136 2.0 TDI 2014.
 

mladen

Registered User
Well today it seemed to get to 70 within 10 minutes, then it took another 10 minutes to crawl to around 77-78 degrees, but no higher even after half an hour. I've also noticed the auto start/stop feature hasn't activate for a while (it comes up with the crossed out A), presumably because its not getting up to temperature. Given that its not getting up to temperature, I'm starting to worry this may affect DPF regen?
 

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777GE90

Registered User
From my experiences, I've had DPF regens start about 5 minutes after pulling away from my driveway in freezing conditions and with the coolant temps still below 50. So don't think that will be a problem to be honest. Similar story with the stop / start system.

But ye if the car is not reaching 90 at all, then something must be wrong.
 

leonwilliams

Registered User
Well today it seemed to get to 70 within 10 minutes, then it took another 10 minutes to crawl to around 77-78 degrees, but no higher even after half an hour. I've also noticed the auto start/stop feature hasn't activate for a while (it comes up with the crossed out A), presumably because its not getting up to temperature. Given that its not getting up to temperature, I'm starting to worry this may affect DPF regen?
On the stop start mines doesn't work all the time. Of I have heater blower on high .If it's on one bet it works every time or if heater is off

Sent from my SM-G935F using Tapatalk
 

IRONy_MAN

IRONy_MAN
Just a thought: my a4 b8 had the same issue for a few days and the car was running fine just the engine temp wasn t going anywhere near 90 so I ve started to check and I ve discovered that the water pump was faulty and the coolant was dripping under the car. Only time when I ve noticed problems with the start stop was on Autobahn and after a few hours of good driving the car failed to pull and the turbo was dead plus the egr valve was all messed up in relation with that. Hopefully is nothing related. Adi
 

SRRAE

Registered User
Where is the thermostat on these cars? Is it behind the water pump?
 

RapidAssistant

Registered User
I went from a B7 2.0 TDI to a B8 2.0TDI and like you I 've noticed the same.....the trip computer on the B7 rarely went below 47-48mpg whilst on the B8 I have now it tends to max out at 43-44 tops. Could be something to do with the way it is tuned - mine is just the "standard" TDI it isn't an "e" or an "ultra". Having said all that I take the figures that come out the trip computer with a pinch of salt really, the real world figure is the only one you can't argue with.

I know that the B8's tank is slightly smaller than the B6/B7s (not sure how it compares with you old one which was a B5) so you are going to get a lower range anyway.

Regarding the temperature reading again - on cold frosty days it never gets to the central position on the gauge, and during the winter months the auto start/stop hardly ever kicks in. But I have had my car for over 3 years, it has been through the Audi computer at the dealer three times for servicing now and it all checks out as normal.
 

SRRAE

Registered User
Are there any writeups on how to do this or does anyone know how easy it is. Do you have to take off the alternator?
I think Im having the same problem. My drive to work takes 30 mins and its about a third town, third country and a third motorway/dual carrage way and the temp hardly goes over 75C.
 

666markyboy

Registered User
As already mentioned, change the thermostat , this will be the cause of slow temperature rising and change the Coolant temperature sender as this is probably faulty , reading low makes the engine management thick the engine is cold so over fuels it which is causing your crappy MPG
 

AudiLeon

Well-Known Member
VCDS Map User
Unlike the older pd engines where there was two parts to the temp sensor. On these there's only one. So if you replace the thermostat and the temp gets to 90 after that. I wouldn't bother changing your cts.

I'm afraid the 2.0cr engine is just **** on fuel. I had a fairly gentle drive round Europe the past 2 years. Covering about 4k in 2 weeks each year. Dash would report over 60mpg. When i filled up. I never once broke 50mpg. My Leon fr with a tractor engine can even manage that.

Saying that though...
350 miles on any assumed 56 litres is 28mpg
500 is 40mpg.
 

mladen

Registered User
Bit of an update, turns out i had a seized caliper. Seems to be back to returning close to 500 from the tank after fitting a new caliper. Coolant temp seems to get to around 82 degrees but still no higher. Although warm enough to allow the autostop to function. Not sure whether i’d still have much to benefit from changing the stat?
 

AudiLeon

Well-Known Member
VCDS Map User
So 40mpgish.
Depressing isn't it for a modern diesel.
 

SRRAE

Registered User
So 40mpgish.
Depressing isn't it for a modern diesel.
I struggle to get 40mpg most days.

I recently got 43mpg, and that includes doing over 300 miles on the motorway at 60mph. That's the best I've ever got.
Mine to has never reached 90C. Even when going up a very steep motorway hill in Wales, it rose to about 80C but as soon as I reached the top of the hill, it dropped to around 70C within a couple mins.
 

CarbonMike

Registered User
So 40mpgish.
Depressing isn't it for a modern diesel.

Yep.

I went from a 2wd 2.0 TDi B7 averaging 45ish mpg every where an over 500 miles a tank, to a Quattro B8.5 with a tiny 55 liter tank that barely breaks 38mpg daily.
 

Jemster

Registered User
Same. B8.5 quattro, barely seeing 32mpg since November when I bought it. However. Since the weather finally got above 12 here (Belfast) it has been a lot better. Got 40 on the DIS last night just on an 8 mile trip around town with ambient temperature around 12-14 degrees. I’d have only seen 33 tops over the last few months on that kind of trip so it’s looking like temperature is going to make a massive difference - that’s a 1-off but I can dream can’t I? :)
 

CarbonMike

Registered User
Yea there not great mpg. I only got mine in January, was expecting lower mpg because of being 4wd but nowhere near this bad.

My wifes Fiesta ST gets way better mpg even if i drive it same way id drive my A4 to work and back!

Im quite disappointed with it to be honest, to the point where ill probably sell it in the next 6 months or less. Shouldve got a TFSi instead lol.
 

piglett

Registered User
On my Exeo, same engine CAGA, there's another "coolant thermostat". I've replaced it with a Behr/Mahle TH 580. Haven't had any issues since. Warms up quick and stays at 90 degrees.
It's located on a hose, above the gearbox. Passes water from the main thermostat to the exhaust heater. Original part is not a thermostat, but a one way valve. Comes as a replacement with the hoses. Cannot be ordered separately. ETKA won't show a part there.

Regarding fuel, please keep in mind that it's a heavy car( old A4s are some 350-400 kilos lighter). And the engine's compression ratio is low at 16.5:1, when the previous PD generation was at 18.5:1.
Fun fact: Mazda's 2018 engines are at 14:1 compression for both petrol and diesel engines.
 

Jemster

Registered User
It's alright saying to keep in mind that it's a heavy car, but at the end of the day, if the manufacturer says it will do x mpg, owners have a reasonable expectation it will get reasonably close to the specified figures (I don't live in fantasy land, I expect some variation! :)). If not, then it is the manufacturer that should bear in mind it's a heavy car when working out what the consumption is, and specify it accordingly.

If you bought a fast car on the basis it was going to do 0-60 in about 5 seconds, because that's what the book says, you'd rightly be disappointed if you found it did it in 8 seconds. That's about the same ratio of wrongness. In that circumstance of course, you would be able to tell from a test drive that it didn't do what was expected. With fuel economy, it's not possible to "test drive" it to find out, as only will it become apparent after purchasing the vehicle.

Wooohooo I got 32.9mpg on the last tank. That's almost 390 miles between refills. So the warm weather has made a marginal improvement at best. Oh well, re-map to remove the emissions fix next...
 

666markyboy

Registered User
I think a lot of it down to conditions and driving styles,,, I have 2.0 CAHA engine in a B8 Avant Quattro ( doesn't get much heavier ) and I drive 80 miles a day, 75 of which is motorway and I can squeeze 50mpg out of it ( Just ) but I have to concentrate and stick to around 55 mph but come the weekend when I'm round town it drops to mid 30's
 

DarthVAG

Registered User
I've had my used 2010 Audi A4 2.0 tdi for almost a year now and noted fuel consumption doesn't appear to be that great at all. Just had a 350 mile return from a full tank, if I do mostly long distance motorway I can squeeze 500 miles out of it. This just doesn't seem right?

I remember my old T-Reg 1.9tdi Audi A4 Avant pushing 800 miles on a long road trip, perhaps 600 miles if ragged it about town. I'd have thought with a more modern engine things would have been more efficient.

The car I have has the CAGA engine code and has had the emissions update by the previous owner, car now covered 150k miles.

The engine coolant temperature takes a good 20 minutes driving to get to 70 degrees, but then rarely passes it. The only fault code from a scan appears to be a faulty Glow Plug No 1, but this shouldn't affect fuel and temp surely?

Previous issues have included an erratic idle (see youtube video), but a new fuel pressure regulator sorted this. Having said that, there is still a bit of very minor idle vibration at times which goes when I give a bit of throttle. Also steering wheel seems to vibrate at times around the 70 mph mark (wheel alignment and balancing hasn't resolved the issue), no vibration at lower speeds. Car is on original clutch/flywheel as far as I'm aware., although no noticeable slip on clutch yet, but flywheel could be suspect?

Seems like a multitude of issues, although engine seems to run fine otherwise. If anyone has any experience in the above issues or could provide any pointers it would be much appreciated.


I have the 2010 A4 B8 2.0 TDI CAGA engine, high mileage and had the problem of the temperature never reaching the normal 90 degrees on the dash. Driving in traffic it would try and reach it, but never quite - then on the motorway it would drop to 60-70 displayed temp.

I have seen lots of posts with people saying these engines have a hard time reaching the standard 90 degree temp, and it's nothing to worry about etc,
but IMHO the engine not reaching the proper temperature would have ramifications on fuel efficiency as well as DPF regens to name a few.

I have today just finished changing the engine thermostat (the 3 port/hose large version - (there's 2 types depending on engine) - it was an absolute job to get to - having to take off various coolant pipes and throttle intake to get to it all... some of the bolts holding the pipes and paraphernalia in place are very hidden and hard to reach, but I managed to do the job in the end with lots of swearing.

I flushed the engine and radiator, fitted the new thermostat (located just behind the alternator into the engine block) and reconnected everything, put new coolant in - took the car for a test drive and the temperature reached the required 90 degrees within about 5 minutes of test drive. It was a sight to behold!! The cabin got nice and warm too immediately, which was another symptom of the overcooling that was going on earlier.

So anyone with the engine running cooler than it should - this is not normal operation IMO, the first port of call is the thermostat in my opinion, it's probably stuck open or not functioning properly. The replacement has solved the problem at any rate.
 

DarthVAG

Registered User
ps: Whilst I had the throttle body/intake manifold off (not sure if this is the proper name for it) I took the opportunity to clean up the built up carbon gunk which had settled inside the unit.
 
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