Guys - I first noticed this last winter and now this winter same story. As soon as the temperature drops below zero, during the first mile, the car refuses to engage 5th gear for the first mile.

Have you noticed the same? My work place is literally on a dual carriageway, so within a minute I will be doing 60mph. Is perhaps the transmission trying to warm itself up? Even in tiptronic mode it refuses to listen. But once it's done a mile it's fine. Weird!

This could be warmup, but it might also be an indication that the power of your car's engine is a bit down compared to stock values.

Basically, auto boxes sense torque produced by engine (sensors in mounts), and if there is not enough torque to ride in 5th, they kick down one gear (or never enter higher gear). Frankly, this coupling of gear changes to (inevitably deteriorating from new) engine torque and power is really annoying, but they do this to provide smooth gear changes and guarantee acceleration in each gear.

I know quite a few people (including some unscrupulous dealers) chip the car's engine at this point to provide increased torque and power (or at least back to stock levels), perhaps it is a good option for you?

If nothing is done, after a while (could be another couple years, though) you will notice that the autobox never actually goes into 5th, or that it goes in and then immediately kicks down.

This could be warmup, but it might also be an indication that the power of your car's engine is a bit down compared to stock values.

Basically, auto boxes sense torque produced by engine (sensors in mounts), and if there is not enough torque to ride in 5th, they kick down one gear (or never enter higher gear). Frankly, this coupling of gear changes to (inevitably deteriorating from new) engine torque and power is really annoying, but they do this to provide smooth gear changes and guarantee acceleration in each gear.

I know quite a few people (including some unscrupulous dealers) chip the car's engine at this point to provide increased torque and power (or at least back to stock levels), perhaps it is a good option for you?

If nothing is done, after a while (could be another couple years, though) you will notice that the autobox never actually goes into 5th, or that it goes in and then immediately kicks down.

I understand what you are saying, but Tiptronic mode should over-rule the default tiptronic pedal demand/ gear change maps, shouldn't it?

BTW, I remember you writing about your tuning map that gives you more top end - how did you manage that - was that a bespoke dyno cal, or something else?

I am seriously considering in the next year or so changing my car to a MANUAL 2.5 tdi Elegance. I keep checking adverts, but suitable ones come up as regularly as rocking horse ****.

I vaguely remember that a tiptronic auto box can override even tiptronic mode if it determines it is not good for the engine (ie too much loading, not enough torque), for sure DSG boxes can do that. Might be worth checking the ECU and resetting all adaptations with VCDS.

Torque limit/sensing problems are why I steer clear of all auto boxes, even though I could do with a long 7-spd DSG one. But I keep my cars for 8+ years, and really do not want to buy a "feature" that will make the car undriveable in the long run. Also, if a manual gearbox goes wrong, it is a lot easier to replace and you get more boxes to choose from (with slightly different gearing).

My 2.5TDI is a manual, so no problems there, and yes, there are not many around.

It was a custom remap, in fact, I went abroad to get it done. But I know from the guy who did the remap that even with an ordinary, quite moderate remap the auto box torque problems go away. But if you do remap, remove pilot catalyst and just leave the main one. Pilot catalyst is quite a drag on the turbo as it is a tad too close to it. You might want to think about removing the front cat first, this might be enough to get the performance back.

Edited 3 February, 201214 yr by dieselV6

Guys - I first noticed this last winter and now this winter same story. As soon as the temperature drops below zero, during the first mile, the car refuses to engage 5th gear for the first mile.

Have you noticed the same? My work place is literally on a dual carriageway, so within a minute I will be doing 60mph. Is perhaps the transmission trying to warm itself up? Even in tiptronic mode it refuses to listen. But once it's done a mile it's fine. Weird!

What happens if you leave the car idling for a while to warm the engine up a bit before you drive off?

I know that my V6 takes about 8 miles of A road driving before the water temperature gets up to normal, and when starting from very cold these days, it sounds raucous (like an old style diesel) for about a minute before it settles down to the the more normal muted tone of the V6. I find that during the first mile or so, the engine seems to want to be treated gently, but after that mile it's fine.

Mine is a manual as well (60k) and I might be mistaken, but the clutch doesn't feel quite so smooth on the take up for the first few gear changes when it's very cold, but after that, it's back to normal.

Obviously with a diesel, the bang is essentially created by spraying atomised fuel onto hot compressed air that has been heated by the compression of the air in the cylinder, the temperature being a function of the compression ratio. On a very cold engine, that heated air must be being cooled by the large lump of very cold metal that the engine has become overnight. I would have thought that this would lead to lower power due to the poor combustion conditions, and I guess that this is born out by the low mpg figures while the car is warming up, as the ECU essentially creates a "rich mixture" to compensate?

Would modern diesel engines actually start without glow plugs in very cold weather, I wonder

What happens if you leave the car idling for a while to warm the engine up a bit before you drive off?

I know that my V6 takes about 8 miles of A road driving before the water temperature gets up to normal, and when starting from very cold these days, it sounds raucous (like an old style diesel) for about a minute before it settles down to the the more normal muted tone of the V6. I find that during the first mile or so, the engine seems to want to be treated gently, but after that mile it's fine.

Mine is a manual as well (60k) and I might be mistaken, but the clutch doesn't feel quite so smooth on the take up for the first few gear changes when it's very cold, but after that, it's back to normal.

Obviously with a diesel, the bang is essentially created by spraying atomised fuel onto hot compressed air that has been heated by the compression of the air in the cylinder, the temperature being a function of the compression ratio. On a very cold engine, that heated air must be being cooled by the large lump of very cold metal that the engine has become overnight. I would have thought that this would lead to lower power due to the poor combustion conditions, and I guess that this is born out by the low mpg figures while the car is warming up, as the ECU essentially creates a "rich mixture" to compensate?

Would modern diesel engines actually start without glow plugs in very cold weather, I wonder

Min had 5 dead glow plugs, and required 3 starts to get it going plus blue smoke, when ambient was 5-10 degrees. One cylinder head and 6 glow plugs later, all good, starts fine even though it cranks slowly - I think the battery is not going to live much longer.

I also find the car sluggish for the first mile on cold mornings - just seems to want to be treated gently. I also find when its very cold if I do stamp on the accelerator because I have to (avoid it though) the power kicks in very violently, from nothing to everything. Well, that's a bit of a 2.5 tdi characteristic, but even more so when cold.

The injection is advanced when doing a cold start, hence more raucous note. Then retards and all smooths out, normal, mine does it too. I know dieselV6 has even set his to the extreme of advance tolerance - adds a bit to fuel efficiency as the fuel has more time to burn.

dieselV6: I wil consider removing the stage 1 cat, but tell me is it access from below or from above, do you recommend just breaking up its contents with a screwdriver or getting a replacement fabricated out of stainless? Or does someone already sell a de-catted pre-cat so to speak?

It would not be the same part as an Audi A6 2.5 of the era, would it? I am just a tad bit nervous about starting to take apart the exhaust of a 10 year old car in case I open Pandora's box!

dieselV6: I wil consider removing the stage 1 cat, but tell me is it access from below or from above, do you recommend just breaking up its contents with a screwdriver or getting a replacement fabricated out of stainless? Or does someone already sell a de-catted pre-cat so to speak?

It would not be the same part as an Audi A6 2.5 of the era, would it? I am just a tad bit nervous about starting to take apart the exhaust of a 10 year old car in case I open Pandora's box!

I think it is the same cat as on Audi A6 2.5 163bhp, I only once saw it on Ebay though, they do not often come up. I looked for decat pipes, but they're not available for 163bhp engines. This cat would be a downright pain to gut out due to angled design, I recommend having the pipe fabricated, cost as much as a used cat on Ebay. Just take the cat to the exhaust shop and ask them to make the pipe of the same layout. The only thing worth mentioning is that the shop should make sure the pipe coming out of turbo is straight for at least 2in or so and that they weld in nuts for bottom flange and for exhaust shield support, otherwise it will be a pain to install.

In this way, if they ever actually start checking diesel NOx emissions, you can put the factory cat back on. PM (smoke) emissions actually go down without pilot cat, because you get about 5% more oxygen in the engine due to smaller back pressure.

The job is relatively simple, but requires access from both top and bottom, and is best to start on a warm engine (and after winter ). Turbocharger side screws/nuts need good soaking with penetrant spray, otherwise they seize and crack while undoing. You need a new gasket for both decat pipe ends. Cat to flex pipe screws are much easier remember to undo bottom exhaust mount as it makes moving the cat around much simpler.

I think it is the same cat as on Audi A6 2.5 163bhp, I only once saw it on Ebay though, they do not often come up. I looked for decat pipes, but they're not available for 163bhp engines. This cat would be a downright pain to gut out due to angled design, I recommend having the pipe fabricated, cost as much as a used cat on Ebay. Just take the cat to the exhaust shop and ask them to make the pipe of the same layout. The only thing worth mentioning is that the shop should make sure the pipe coming out of turbo is straight for at least 2in or so and that they weld in nuts for bottom flange and for exhaust shield support, otherwise it will be a pain to install.

In this way, if they ever actually start checking diesel NOx emissions, you can put the factory cat back on. PM (smoke) emissions actually go down without pilot cat, because you get about 5% more oxygen in the engine due to smaller back pressure.

The job is relatively simple, but requires access from both top and bottom, and is best to start on a warm engine (and after winter ). Turbocharger side screws/nuts need good soaking with penetrant spray, otherwise they seize and crack while undoing. You need a new gasket for both decat pipe ends. Cat to flex pipe screws are much easier remember to undo bottom exhaust mount as it makes moving the cat around much simpler.

Thank you dieselV6.

There are quit a few on German ebay, here's one for your engine :yes: :

BDG Kat

I definitely fancy the idea of increasing the airflow into my engine!