poor fuel consumption

[dieselal]

I have a 2002 a6 1.9 tdi sport and have noticed that when I put £10 worth of diesel in the tank, I only managed 95 miles whilst driving steady and mostly at 70 mph on the motorway.
Is this correct for the vehicle, mileage is 82000 and full Audi service history?
I did have a water temperature reading start to go erratic last week for about half an hour, read 90, then dropped off to minimum , back up and down, like I was at the bermuda triangle, However this is now normal again.
It is due for service in 3000 miles, any suggestions?

[dieselal]

Had the car scanned and no faults showed.The problem has only recently been happening, ironicaly, the same time my engine temperature display started going haywire, as if I were at the bermuda triangle.Bought a new sender today, GREEN not black as original one is, ( been superceded ) just waiting for the engine to cool down before fitting.
Apparently, this temp sensor can cause a multitude of faults, one being poor fuel consumption, as the ecu is fed with info from 2 of the 4 pins in the sender , and the dash display is sent info from the other 2.Although the reading EVENTUALY creeps up to 90 degrees after morning start, it is not necessarily reading that at the ecu.

[onzarob]

Common fault. Since its a dual sensor the ecu side could be doing the same. let us know how it goes after the change.

Rob

[dieselal]

So much for the so called VW trained mechanic that showed me the wrong sensor, I ended up taking off the oil sensor with 2 pins, will take it to garage in the morning because it was almost dark when I finnished.

[dieselal]

Fitted the new sensor this morning, located at the rear of the engine. After starting, the car gradually rose in temperature until it reached 90 degrees.No more flat spot pulling away in 1st gear and the car feels more responsive.I cannot understand why there was no fault code thrown up when scanned? Perhaps , because there was a reading , however wrong, the ECU suspected all ok?
Should start getting the proper fuel consumption now, but even better, no worry about too much fuel passing through unspent.

[dieselal]

ARGH!!
The car is still not doing what it should mpg?Also noticed some light greyish coloured smoke during hard acceleration, and a flat spot in first when initialy pulling away, worse with cold engine.
I would have hoped for a little more advice from this website, but all I can do now , after putting a diesel cleaner through, is change the maff, even though no codes showed up, but they don't always show a fault when failing.
Still IF there IS anyone out there, A little help would be very gratefuly recieved.

[AlexS]

Hi dieselal

I have a passat with a very similar problem.

engine 100hp Y-reg 2002, 130000 miles fsh
no faults on computer from local garage and VW garae
changed - AF meter, Cat, all filters, thermostat (it was taking a long time to warm up)


I am lucky if I get much over 45 mpg with stupidly slow driving (never going over 55mph on a long dist). If a drive normally it goes below 40mpg. I tried a same rout with a friend of a slightly older passat (the 115hp Sport) and he was getting 10 to 15 mpg more. Another frend in a Skoda with the same 100hp engine gets 15mpg more!

Symtoms are exactly the same, slugish when cold, some exhaust smoke.
Generally mpg not too bad at long high speed runs.

I have had the car for 2 1/2 years and the probelm is slowly getting worse and worse

How long ar ethe injectors meant to last on the more modern cars, do the breakdown etc and do they need repacing? I guess they are not cheap.

Cheers

Alex
(first post - please help too)

[onzarob]

Hello, Both your cars have PD engine and the injectors are v espensive as they from part of the pump. I think they cost around £400 each!!!!

I'm no expert on these engine, but i have read they do suffer from camshaft wear as it drives the injectors. Maybe worth checking it out. usally the symptoms are power loss and rough running.

A faulty MAF can cause whiteish smoke as the ecu is unable to read the airflow correctly. this has a knock on effect of causing incorect fuel amounts being put into the engine.

Another issue could be warn turbo seals or the varible vanes of the turbo sticking causing to car to stutter as you described. Unsure how to test this without taking it off the car, someone around here may be able to help with this.

Rob

[dieselal]

Thanks for the reply AlexS, Injectors should be good for 100k plus, the cheapest place is actually Euro car parts for replaciong them.
My A6 tdi has now done 87,000 miles and has been fully looked after by Audi from new, I am having the service done elsewhere this Thursday, although, I have bought the oil (new castrol slx 3 longlife 5w30) from main dealer along with air, fuel and oil and pollen filters.
I did change the engine temperature sensor last week due to faulty original, they are now green instead of black, and the temperature is rising from a cold engine very steady fro 0-90 degrees, thought that was the actual problem but obviously not.
Still, I hope by changing the filters and the service, things should improve, if not, I will change the mass air meter, Bosch from Euro car parts, £68 total. with £20 surcharge, I'll just take the old one off outside and swap straight over.

[dieselal]

Thanks onzarob,
I've a strong hunch it is the maff, I can't notice a power loss as the car pulls cleanly through the gears, but my previous car was a Bmw 530d, and I'm still getting used to the slower engine. The whiteish smoke is making me look toward the maff, especially as no codes were present when scanned, even the faulty engine temp sensor didn't throw up a code , because it was still working and giving A reading however wrong it was.
The hesitation on pulling away could also be maff , as my Bmw did the same , I changed it and all was well again.
I'm only getting about 40 mpg and that is some town and motorway driving, at night whilst driving as economicaly as possible.