TDI 130 Poor MPG

[skymaster]

I drive a 2003 TDI 130 A4. I have owned is about a month or so and I was expecting better MPG than I am getting at present. I have been very light on the right foot, very gentle with it when cold and rarely rev about 3.5k on the rev counter.

It's just had full service with longlife oil, fuel filter, oil and air filter. I cant seem to get any better than 38 mpg. I took it for a 35 mile run at the weekend and expected to get better.

Any thoughts or ideas?

[andyroo]

Hi
I've got a similar Avant with Multitronic and average 36mpg the gearbox is not to blame as Audi quote very similar figures for both.
Just changed the air filter to a K&N panel replacement. This has reduced the smoke output to zero and so far looking at at the mileage used versus the mileage left (I dont have one of them computer thingys) it's looking promising for a reduction in fuel consumption I'll repost when I fill up and calculate properly brim to brim.

Andy

[vaslam1986]

I had the same problem....when i bought the car i would average around 45mpg but recently I get on average somewhere in the 30's and if i throttle it i get mid 20's maybe less. I got told it can be a couple of things firstly the your temp sensor can be on the blink. This is cheap to replace the other problem that I know of is the more dearer one...one of your injectors mayb on the blink...you can try a injector cleaner when u next tank your car and see if it improves the mpg or one or all of them may need replacing.

[skymaster]

Would either of these manifest themselves in any other way? A lack of power or lumpy idle? Mine seems to be OK in terms of power. Although without driving an identical car back to back how is one meant to know what is 'right'

If I wanted to ckeck to see if these things were at fault how would I go about it?

[vaslam1986]

Would either of these manifest themselves in any other way? A lack of power or lumpy idle? Mine seems to be OK in terms of power. Although without driving an identical car back to back how is one meant to know what is 'right'

If I wanted to ckeck to see if these things were at fault how would I go about it?

In terms to power you should be ok...but im pretty sure both problems will show up as being lumpy on cold and idle. your best bet would be to get it on the VAG-COM and get the fault codes. I'm sure someone on here would be more than happy to help you.

Sorry I couldn't be of any further help.

[skymaster]

Could thermostat be playing up? Does anyone think?

How long should it take for this engine to warm up to normal operating temperature? I find I have to drive for at least 20 mins before the needle is central in the temp gauge..

[andyroo]

Well i've filled up now and low and behold MPG is the usual 36 What next i've run the vag on it and there are no faults showing but as I keep pointing out this is a normal run of the mill car not an F1 so no where near all parameters are monitored. These so called"technicians" do not seem to able to think beyond "the computer says no".

[skymaster]

I think my problem could be a stuck open thermostat. My engine seems to take forever to get warm. I drove roughly 5 miles on thursday to my mates garage. He opened the bonnet and the coolant was stone cold, radiator stone cold and also a pipe he expected to get hot was also stone cold. He thinks problem could be due to this and has reccomended fitting a new thermostat.

[skymaster]

Roughly how long does it take for your TDI 130 engine to reach full running temperature?

[Teutonic_Tamer]

I think my problem could be a stuck open thermostat. My engine seems to take forever to get warm. I drove roughly 5 miles on thursday to my mates garage. He opened the bonnet and the coolant was stone cold, radiator stone cold and also a pipe he expected to get hot was also stone cold. He thinks problem could be due to this and has reccomended fitting a new thermostat.

Good heavens, a diesel could reasonably take longer than 5 miles to reach normal operating temperature in this weather!

The fact that the rad was stone cold actually proves the thermostat is OK. They are held closed by a hoofing great spring, and hot water causes a sealed wax pellet to expand, pushing the stat open beyond the spring pressure.

Simple test, but long winded, and DISCLAIMER - keep scarves, neck ties, animals and children away from moving engne parts. From a stone cold start, start the engine. Whilst it is ticking over, lift the bonnet, look for the large coolant hoses which go to the rad. One will be near the top of the rad on one side, the other will be near the bottom on the opposite side. Now look for two smaller diameter hoses headding into the bulkhead - these supply the interior heater. Carefully feel all hoses, they should all be cold. Sit in the car, watching the temperature gauge. As soon as you see it rise, check all 4 main hoses. The two smaller heater hoses should get warm first. The larger hoses to the rad will remain stone cold, until the temp gauge is very close to the normal temp. The heater hoses should get hotter and hotter. When the temp gauge does get near the norm, the top hose to the rad will suddenly get warm very quickly, as the thermostat reaches the required temperature, opens, and allows the now hot water to the radiator. The bottom radiator hose should soon get warm after this.

That is perfectly normal cooling system operation, and is perfectly common for the radiator to remain stone cold after relatively short journeys!

Sadly, if you want your interior to warm up quicker in the winter, get heated seats, or a petrol engine!

Rgds