Very high fuel consumption Audi A4 B6 ALT 2.0 Engine

**cmulindwa** · 20-10-2014,12:54 PM

Hi All,
I am hoping someone can help me here!!
I have a 2004 A4 B6, ALT 2.0 petrol engine with 94,000 Kms on the clock. The engine runs smooth and is regularly serviced - good spark plugs, good air cleaner, etc... But I only get about 14 MPG (6Kpl) for town runs and about 19 MPG (8Kpl) when out of town!!!!
I recently put in a new MAF sensor thinking it would improve my fuel economy but it didnt.
I use the Audi recommended tyre size and tyre pressure. I also use shell V-Power fuel only (98 Octane).
My exhaust pipe has deposits of black soot on the inside but the car does not smoke.
I a recently changed the brake vaccum boost pump, which had failed. I nitially i thought this was causing the high fuel consumption, but even after i replaced it the consumption remained very high. I have tried to look around the engine for vaccum leaks without succeess. The engine idles well.
This incredibly high fuel consumption is draining my pockets. Does anyone know what the problem could be or what i should look out for?
Best regards
Charles

**mikeybutch** · 20-10-2014,07:35 PM

It seems this engine can be thirsty.I easily get 50% more from my 2.5tdi auto and often a lot more.Have you checked that the brakes are not binding and clutch not beginning to slip: both can easily drop mpg .

**pauldazzle** · 21-10-2014,01:23 AM

Coolant temp sensor is also worth checking out as it's a very common failure, & causes the ECU to fuel incorrectly if it's goosed.

**cmulindwa** · 21-10-2014,05:51 AM

Thanks Mikeybitch, a very thirtsy engine indeed.
I checked all the brakes and none is binding, what i am not very sure about is the clutch and whether it is beginning to slip. I noticed the last two times that diagonistics was run by my mechanic, that the clutch adaptations were out and had to be re-done. On each occassion we went through the adaptation "start - stop" procedure without a problem. There were no errors registered on the clutch. Without any error codes being registered are there any other symptoms of a slipping clutch that i should look out for? How easy is it to change the clutches? My tranny is a Multitronic CVT!! I understand there was an upgrade of the clutches around 2004.
Many thanks again
Cmulindwa

**cmulindwa** · 21-10-2014,06:03 AM

Thanks Pauldazzle,
I will check the coolant temp sensor. I have recently noticed though that my coolant level keeps dropping very slowly. I once got a coolant level error on my dash board, topped up and have since noticed that the level drops very slowly over. This is a new problem. My engine run for over 30,000Km without ever topping up on the coolant. Could this be related to the Coolant temperture sensor?
Just to note that my temperature seems to be steadily at 90, it falls down a bit from time to time as i drive on a long journey, but I have never had any over heating. Would the CTS normally throw any diagnostic error codes if it failed?

**pauldazzle** · 22-10-2014,10:07 AM

CTS failure wouldn't cause coolant loss.
For your info. CTS has two outputs, one to the dash & the other to the ECU. Unfortunately it's common for one output to die without effecting the other. Furthermore, as is the case with several engine sensors as long as the ECU is getting a signal it won't throw a code so you can't rely on fault codes for diagnosis. Instead you have to look in VCDS engine measuring blocks to see whats going on. If you have the old black type CTS fitted I would change it for a genuine VAG revised green CTS regardless as the black ones always fail at some point.
Temperature should get up to 90c & stay there so any downward fluctuation would suggest a sticking thermostat.

**cmulindwa** · 22-10-2014,12:56 PM

Many thanks. I will change my CTS to a green one as advised.

**Doc B** · 22-10-2014,09:03 PM

When you change the CTS make sure you fit a new o-ring as they wear/perish & cause coolant loss - usually very slowly.....

**cmulindwa** · 23-10-2014,05:22 AM

I will do. Many thanks.

**cmulindwa** · 14-11-2014,05:33 AM

Thanks Pauldazzle,
It turned out i already had the green CTS, but I changed it anyway.

Now I seem to be having the dreaded CVT trouble!!

A few days ago as i was driving, i noticed the letters PRND in my dashboard all light up at the same time. They lit up steadily without flashing. In great shock i stopped the car and when i started the engine again the PRND light cleared for a while and came on again intermittently. All along the car was driving fine and the gears shifting ok with no trouble at all.

I noticed however that there was a rattling sound coming from under the bonnet - it sounds like a small diesel engine. The sound is steady - it does not change when i shift gears or rev the engine. Went underneath the car to try and find out exactly where it came from, but couldnt pin point the source - am not really sure if its coming from the gear box or if its caused by a broken engine mounting.

I noticed that both my engine mounting have leaked and need to be replaced, but am also worried that it might be coming from inside the gearbox

2 days ago i went to my mechanic, and using his VCDS he found one fault code 18149 - "Clutch Pressure Adaptation Limit Reached". He cleared the code. The warning PRND light has not returned since but i still have the rattling sound.

Might you know what "clutch pressure adaptation limit reached" means or what i should check for? Do you think changing the ATF oil would address the vibration? Could it have something to do with the clutch pressure plate? The gears still shift fine. Will be most grateful for some advice, I dont have any good knowledgable CVT mechanic in my area!!