Audi A4 B6 1.9 TDi poor fuel economy !

[Stefan Paiu]

Hi everyone,

I have just joined this forum and I am hoping someone can give me some clues as to where to find the solution to my problem.

I am getting very poor fuel economy on my 2003 Audi A4 1.9 Tdi (5 gears manual, 101 BHP, no modifications to it). I am getting an average of 25-30 MPG urban (Birmingham) and this if I drive it as economically as possible. On motorways it goes to about 45 MPG. I know this car should do 40 MPG without any problems in the city so there's got to be a problem somewhere. I have already removed the MAF sensor and cleaned with no luck. There is no loss in power as the car pulls really well.

I was hoping that maybe someone in Birmingham can help me hook it up to VAG com and see it there's any errors showing. Also, it's probably unrelated but who knows, the ESP module keeps coming on at random times and wouldn't go off until I turn the engine off.

Any advice would be greatly appreciated.

Thanks,
Stefan

[pdlh]

Hi Stefan,

I've no idea if this helps, and I have the 130 BHP version 5 speed, on a 52 reg, so slightly different setup but for the past 2 years I've suffered bad fuel consumption, I had it serviced, no difference? was only doing 485 miles on a full tank of fuel, compared to the original 650 it used to consistently do. No faults appeared on VCDS scans, engine all running fine?

Only thing I noticed was it burned out a set of front brake pads in about a year 8 - 10k miles. The garage said the front caliper had stuck on, great cost for a new caliper, pads and discs. Even after it was done, I thought the front left side always ran hotter than the right. 9 months later, another set of brake pads burned out only on the front left. This time garage replaced brake master cylinder and servo. Overnight difference, Fuel economy back to 600 plus miles on a tank of fuel.

Garage said the brake master fault was quite common on the 2002 - 2003 age cars.

Not sure if it's the same problem on your car, but might be worth seeing if your front left wheel is hot?

The only thing that makes no sense, is why all the brakes did not stick, I don't know why it only affected the front left?

Paul

[Stefan Paiu]

Hi Paul,

Thanks very much for your reply. I took the car for a ride today but didn't notice anything wrong with the brakes. When I bought the car in August it was shaking when braking from over 60 mph. It was due to the front brake discs being warped but I had them changed and the mechanic didn't notice anything else unusual.

What I also noticed recently is that the water temperature doesn't rise to 90c. I drove around 10 miles and the temperature went to 70c, without having the heating on. Could this lead to the car doing 25 mpg instead of 40? It seems like a huge difference. Nonetheless, is it worth changing the thermostat? This is my first diesel car so I don't really know how long it should take to warm up.

Thanks,
Stefan

[arman123]

If the car not getting up to temp 90 and staying there then your state could be stuck open overcooling engine hence crap mpg change the state for a genuine one and the coolant temp sensor when you get the state changed make you tell them to check the state housing that the lugs that hold the stat in have not been damaged the stat twist in the housing and locks in place with the gasket coolant temp sensor is a bit of a tight job just at bottom of bulkhead make sure you get genuine one and the gasket that goes with it and the clip that hold it in place clip is very easy to break do buy two change these items and your mpg should improve a lot

[niall campbell]

you could also blast the exhaust out to de-coke it. Just stay in 2nd gear and run along the road with the revs just under the red. Watch all the black crap coming out your exhaust.

[Stefan Paiu]

I've tried blasting the exhaust as niall suggested and it seems to have helped a little bit. On a 10 mile journey with almost no traffic I managed 32MPG this morning but didn't let the engine go past 2000RPM. The temperature still doesn't get past 70c but the mechanic I usually go to is on holiday for 3 weeks and I have to wait until he comes back. I also asked someone another mechanic about the temperature and he said that as long as it gets to 70c it is fine, as some cars run cold. What I have also noticed is that the mpg drops radically when the car is not moving or when it's not in gear which i know it's normal but still it seems too much.
I don't know if it's relevant or abnormal but when in first gear with very little or no acceleration the computer shows 10-15MPG.
I would change the thermostat myself but I've read that you spill about 1-2 litre of coolant and I don't want to spill it al over the road where I live as I don't think it would make my neighbours happy.

Any other thoughts? Or any good mechanic in Birmingham that could have a look?

Thanks,
Stefan

[arman123]

Frontier Volks Works 52 Cherrywood Rd, Birmingham, B9 4UD 0121-773 9396
try these guys really good

[niall campbell]

why don't you let engine go above 2000 rpm ? Having a turbo in a diesel car helps the fuel economy and by using low revs , it may not be kicking in . You could try using an additive in the diesel fuel as well. In my A 6 I am getting 44 mpg at ten mile point when going to work , however I start really early and hardly meet another car. My car has just opened up at 40,000 miles and on the motorway I am getting 62.3 mpg at 50 mph. I would also look at your air filter and diesel filter to be changed before spending money in a garage. Don't be worried about a diesel car sounding noisy and changing up gear , just don't let it get so high you are thrashing it ! You will still be saving money compared to a petrol car

[Stefan Paiu]

why don't you let engine go above 2000 rpm ? Having a turbo in a diesel car helps the fuel economy and by using low revs , it may not be kicking in . You could try using an additive in the diesel fuel as well. In my A 6 I am getting 44 mpg at ten mile point when going to work , however I start really early and hardly meet another car. My car has just opened up at 40,000 miles and on the motorway I am getting 62.3 mpg at 50 mph. I would also look at your air filter and diesel filter to be changed before spending money in a garage. Don't be worried about a diesel car sounding noisy and changing up gear , just don't let it get so high you are thrashing it ! You will still be saving money compared to a petrol car

I don't let the engine go over 2000 RPM because I noticed that the consumption tends to be lower if I do so. If I change gear at 2500 for example I get around 22 MPG compared to 26-27 if I change at 2000. I will get my filters changed this week and see if it helps.

[niall campbell]

Changing the diesel filter is a must coming up to winter. If theres any water in it , it will freeze. That's the problem with putting cars in for a service , trusting that ALL filters are changed. Keep us posted !