[Johnefyn]

It happened when I was overtaking, the first time it was a hesitation at about 3,250 rpm, then it picked up and continued accelerating. I tried it again and it hesitated twice while going up the rev range, the second hestation was at about 3,750, but with reduced acceleration above that speed. Up to that speed everything seemed fine.

The engine management amber light was on on the time, we have had that before following a week or so of use by the wife to commute half a kilometer or so to and from work and our local Audi dealer had said it needed a blast to clear the system out (not his exact words) and so I wasn't unduly worried about that.

What could it be?

 

[wja96]

It does sound like it could be the DPF. You need to take it for a LONG drive at at least 3000 rpm - maybe only use 4th gear on the motorway for 20 miles or so. That's the only way you'll know, other than plugging it in to a VAS machine to see the DPF status.

 

[Johnefyn]

DPF- Diesel Particulate Filter?? No, just guessing, really. The last time this particular warning came up I didn't notice any power loss, I took it for a thirty mile thrash and and it was OK. This VAS machine, is it something any garage might have these days, or just Audi dealers?

Sorry, I'm obviously not very clued up on what I have under the bonnet, things were very different when I were a lad. Actually, there was a lot less under bonnets in those days.

 

[TT-TOM]

Could be many many things but my mates had a flat spot in the middle of the rev range on his TDI and i suggested a new MAF and it fixed the problem.

 

[Johnefyn]

What's a MAF? sorry!

 

[TT-TOM]

Mass Air Flow sensor, this measures the airflow so the ECU can decide how much fuel to inject and can cause all kinds of problems if they go wrong.

They can be expensive though.

 

[wja96]

VAS machine is the Volkswagen-Audi-System (VAS) and it's the Computer the dealers plug your car into.

You can buy software called VCDS which does 99% of the same things. Many people still call it by it's old name - VAGCom.

It may well also be the MAF, but as I understand it the DPF is a more likely cause. It tries to regen several times then basically cripples the car.

 

[LEO-RS]

Your wife drives 500 meters to get to work? Tell her to use her legs :lol:

Certainly looks like DPF issues. If it's not that, Is your clutch ok? By that, I mean, when you accelerate, are your revs and speedometer in sync? Slipping clutch would show a rise in revs but no increase in speed. You would feel a hesitation until the clutch bit again.

 

[Johnefyn]

Your wife drives 500 meters to get to work? Tell her to use her legs :lol:

Fair comment! In fact I had written half a mile and meant to change it to a kilometre but didn't quite manage it, the fact is that as we had such crap weather she took the car. Apart from one day, that is.

On that day she took the kids in her class up the Eifl (aka "The Rivals") to Tre Ceri at 1,800ft to a stone age fort and took three groups around the encampment, she was in a better state than any of the kids afterwards, including the lad that plays rugby for the county! The kids were well impressed, her street cred is way up now. :mrgreen: Two days after she retired at the age of sixty two! I'll carry on and add that she had two replacement hips five years ago and is like a mountain goat. She's a good 'un!

 

[Johnefyn]

VAS machine is the Volkswagen-Audi-System (VAS) and it's the Computer the dealers plug your car into.

You can buy software called VCDS which does 99% of the same things. Many people still call it by it's old name - VAGCom.

It may well also be the MAF, but as I understand it the DPF is a more likely cause. It tries to regen several times then basically cripples the car.

No, the car was in no way crippled, it's just that there was this hesitation at between 3 to 4 thousand rpm - I don't think for a minute that is was in a "get you home mode" or anything like that.

 

[Johnefyn]

... If it's not that, Is your clutch ok? By that, I mean, when you accelerate, are your revs and speedometer in sync? Slipping clutch would show a rise in revs but no increase in speed. You would feel a hesitation until the clutch bit again.

No, I don't think it's the clutch, but I'll make a point of listening out for any rise in engine rpm when/if it happens again.

Oh, and thanks for all the responses, folks, most helpful, cheers!

PS I've just found out that my local garage has some computer thingy that will do the same job as VASCom, I may pay him a visit if the DPF doesn't get its act together.

 

[TT-TOM]

500 meter trips are not a good idea if you have a DPF.