Wierd very intermittent acceleration problem...

[dukey406]

Hi,

On a couple of occasions in the last month on the 2.0HDI 110, I've come off the pedal and pressed back down again to
find that the car doesn't 'respond' to the throttle.
It doesn't cut out and no warning messages flag up.
By not responding, I mean will not accelerate, throttle doesn't seem to 'work'???
Coming off the pedal, neutral for a min and try again and car drives ok.
Fuel consumption seems high too, 290 miles on £45 @ £1.38/litre?

And help muchly appreciated....

[highlander]

Fuel consumption seems high too, 290 miles on £45 @ £1.38/litre?

So you got 290 miles on 32.6 litres of fuel? That's 8.9 miles per litre. Given that the 406's tank is 70 litres, you're getting 623 miles to the tank, or an average of 40.3 MPG.

It does sound a little bit low for an HDi 110 (which is supposed to give a combined cycle of around 50 MPG) but it depends very much on a number of things, like:

- amount of time spend idling (sitting in traffic, especially)
- how much weight the car is loaded with
- how heavy your right foot is when there's no traffic around (are you a smooth driver?)

I don't know about your accelerator problem, but I wouldn't worry too much about the fuel economy.

[steve_earwig]

If only I think I'd be heading for the connector on the throttle pot first.

[dukey406]

Cheers for replies, I did read about the throttle pot but wouldn't that flag an error code?
I'll have a look in the morning, it's a lovely motor but the electrical side of things leaves a lot to be desired!

As for fuel economy, I have the odd readout fuel guage -I put in £50 from 'empty', did just over 200 miles, light comes on, filled up with £20
and now it's right back up just below half a tank oh well at least she's got some in!

[steve_earwig]

That's the problem, almost everything should bring up the eml, even if it's just anti pollution and tells you nothing else other than there's a fault. I can only think that the engine management isn't seeing the fault because there's no short circuit or whatever that it's programmed to look for.

HDi fuel gauges are always laughably inaccurate, my own particular variation is it'll gradually drop to empty, bring up all the "time to fill up" warnings and then I've suddenly got half a tank. Not always though so you can bet the first time I don't take it seriously I'll end up walking home.

[martint]

Mines is spot on to the tenth o a mile nearly. Just over 40 could be normal in this cold weather. Don't listen to cold air bein better for diesels. They are so slow to heating up & if ur journeys are quick/short, then 40 ain't that bad. Could be worse-my 1.6 passat only gave me 24mpg.
40.mpg ain't bad. I'll bet u in the spring it'll go back to 46!!

[highlander]

HDi fuel gauges are always laughably inaccurate, my own particular variation is it'll gradually drop to empty, bring up all the "time to fill up" warnings and then I've suddenly got half a tank. Not always though so you can bet the first time I don't take it seriously I'll end up walking home.

My old petrol saloon was funny with the fuel gauge - I would brim the tank before a long journey (Aberdeen to Thurso, about 210 miles) just on the way out of Aberdeen, before I hit the A96, and it would be at least 70 miles before the fuel gauge started to come down from "F". But then it would go down quite quickly, and it would be at 50% at around 200 miles. I would then be able to make the return journey without filling up, and the gauge would still show around 20% after having covered 420 miles. The remainder would last me on my 14-mile round-trip to/from work for another week, giving me another 70 miles before the "fuel low" light came on, so 490 miles to a tank. That old car did 590 miles to the tank before the light came on once (nothing but long winding single-carriageway A-roads on that trip).

The Coupe fuel gauge is a lot more accurate, it seems.

[dukey406]

Just for archives, I remedied the problem by cleaning out the Air Doser assembly, as it was intermittently sticking shut!