I thought I'd start a new topic as both these issues seem to be linked together on my car, which I've had for 18 months. (115k 2012 Octavia Scout Mk2 2.0 tdi).

 

Symptoms:

Cold temperatures and/or dry weather (-5 to +5 DegC): Car sometimes decides to increase revs from 750 ish to 950-1000rpm. Also the area around the engine bay starts to really smell of diesel. (Aircon not turned on). Turning the engine off will sometimes clear the fault.

Warm temperatures & wet weather (+5 to +15 DegC): Ditto. Note, it doesn't seem to happen above 15 DegC air temp.

 

Having done lots of reading tonight, & taking these symptoms into consideration, I'm suspecting that there may be some water/moisture shorting something out.

• Possibly one/both of the engine temp sensors,

• Possibly the radiator fan switch temperature sensor,

• Possibly the fan control module itself.

• Might even be a loose connection, or

• A rusty earth connection or 11.

 

Has anyone had the same problem before and if so which of the above was it? With the approaching hurricane Lorenzo and the rather wet conditions, I'm not going to be investigating anything until the weekend at the earliest, so a "starter for 10" would be appreciated.

 

Thanks

Sounds like it's performing a DPF regen given the idle speed changes and fans come on...

 

Alternatively, it could be raising the idle to counteract electrical load. Is the battery original?

It did a DPF clean a few months ago, so I dont think it's that (wish it was!). I do quite a lot of motorway mileage so tend not to get this problem. (1500 miles to be done this week alone).

 

Can't see what electrical load it's trying to counteract to be honest. Seems odd that it's been doing it today; 15 DegC and pouring down.

It was that.

Despite spending lots of time on fast roads the car may still decide to perform a regen at the end or even start of the journey...

 

Why did you get the DPF cleaned, was it preventative maintenance or due to an issue and were the DPF sensors reset? Given that style of driving the DPF should pretty much take care of itself.

 

I'd start with a scan using VCDS or similar. Assuming there are no fault codes, it might be worth logging your calculated/measured soot levels over a few drives. Grab the oil ash level too while you've got diagnostics connected.

30 minutes ago, langers2k said:

Despite spending lots of time on fast roads the car may still decide to perform a regen at the end or even start of the journey...

 

Why did you get the DPF cleaned, was it preventative maintenance or due to an issue and were the DPF sensors reset? Given that style of driving the DPF should pretty much take care of itself.

 

I'd start with a scan using VCDS or similar. Assuming there are no fault codes, it might be worth logging your calculated/measured soot levels over a few drives. Grab the oil ash level too while you've got diagnostics connected.

Just to clarify, I didn't get it cleaned, the car did it itself. 15 minutes at the appropriate revs and it cleared the warning light.

 

With regards to possible error codes, the car has spent many hours plugged into the local non-franchised specialist (Audi master mechanic) and their computer couldn't find anything wrong with the car.

 

You may remember that summer 2018 I did a post about swapping the thermostat? Well it's still misbehaving in the same way. The garage suggested that it could be a temperature sensor or the fan control module, so those are prime suspects. But I'd rather hit the right one first time around if possible.

Cool, just a terminology issue. I've no idea how much you know about DPF's so apologies if this is just repeating stuff you know :)

 

A DPF is basically there to catch soot particles, eventually, the DPF will fill up with soot so every so often, it will need to regenerate where the soot is burnt off. When the soot is burnt off it leaves some residue called oil ash. In a car that's working normally, it's the oil ash that will increase over time and eventually fill the DPF making it unusable.

 

There are a few different types of regeneration depending on soot level:

- a passive regeneration will occur 'naturally' when the DPF hits a certain temperature, these may or may not happen depending on driving style/load etc

- at 18g+, the ECU will trigger an active regeneration, this injects extra diesel to force the DPF temperature high enough, I believe this is also done on distance (every ~400 miles?)

- at 24g+, the car will request a customer initiated regeneration drive, this is because the car was unable to successfully perform an active regeneration, the DPF light should illuminate

- at 40g+, it'll need a service regeneration or forced regen, this is normally done by a garage using diagnostic equipment in a 'safe' area, the glowplug, DPF and ECU lights should illuminate

- finally, if the DPF hits 45g, it's no longer safe to regenerate and the DPF will need replacing

 

Quick graph curiosity of VW:

 

The symptoms you're currently describe match an active regeneration whereas your previous issue matched a customer initiated regeneration drive. Both are different from cleaning a DPF which normally involve removing it from the car and using water/chemicals to remove both soot and ash.

 

Given there are no fault codes, it does sound like you need to do some live logging over a few journeys to try and see what's happening. Genuine VCDS would be my choice but it's not cheap, you might be better with OBDeleven or even a bluetooth OBD2 dongle and the VAG DPF app (if you have an android phone). If there are sensor issues, it certainly can cause missed or possible excessive regeneration's.

 

Do you know if your car has had the 'emissions fix' applied? If so, one of the side effects of reducing the NOx is to produce more soot which inevitably causes more frequent DPF regeneration's.

 

Very quickly back to the electrical load, if the battery is beginning to weaken, the headlights, heaters, wipers, rear demister could be enough to cause the voltage to drop and the rev's to rise to increase alternator output. I'll give my car a few minutes when I start it this morning to see what the idle speed does, although I also have a retrofitted PTC heater which consumes lots of power...

Thank you for that Langers2k. Yes, the last DPF clean situation sounds like the 24g+ example above, so we'll see what happens this week.

 

VCDS, etc; Any advice on where to get one from?

 

Re the NOx software update; I've no idea as the specialist doesn't appear able to determine if this has been done. (He's an Audi centre to be fair). A trip to the local dealers will be required sadly.

 

Battery; pass. I'll have to have a look through the service folder (hugely detailed) to see what's been done so far.

You'll never guess what has just (2 minutes after my last post) lit up on the dashboard.

 

DPF clean lamp. Ah well. LOL

 

Thank you very much for all your help!

Super easy to check for the NOx update - you need the engine software version. If it's above around 9970 (from memory) then it's had the fix.

 

For genuine VCDS, ilexa or gendan are perfectly fine and a 3-VIN HEX-V2 should be around £225. With live logging it's possible to various values from the ECU while you drive. Here is a graph I made a couple of years ago showing some stats during an active regeneration:

 

You can see the regen counter (dark green) start to increase and shortly after the exhaust gas temperature rises and the soot mass (purple and light green) drops. Once the regen has completed, the KM since regen then gets reset.

 

 

I'm surprised that you've got the DPF lamp illuminating given the distances your covering and that CR engines are normally pretty good to their DPF. Have you been doing any short journeys since your last long distance drive?

 

For example, I have a '61 plate CR140 (unfixed) which has covered 178k, the last 130k has been under my ownership. I have a 50-55 mile commute (each way) along single/dual carriageway A-roads with stop/start city traffic at one end and I've never once had the DPF lamp come on. In the last five years, I've probably had the fans stay on less than a dozen times.

 

It makes me think something isn't completely happy in your car but if there are no fault codes, it could be tricky to track down. If you do go down the VCDS route, I'm happy to do some logging if you need something to compare with :)

11 minutes ago, langers2k said:

It makes me think something isn't completely happy in your car.

 

Could be so if the DPF regens happens way to often. Might be way too much fuel injected or so.

If you want to see if your car has had the emissions software update, look for a sticker near the spare wheel bay showing 23R6.

If it is there, then you can expect DPF regeneration at about every 250 miles. 

 

 

Thanks folks. I'll have a look for the sticker in the morning.

Yes, loads of little short journeys alongside the long ones.

No faults logged, but it was quite happy today after the lamp came on for a few miles before I drove from Cheshire to Birmingham. Seemed perfectly happy driving around Birmingham and back to Cheshire tonight also. Same journey tomorrow before heading on up to Glasgow tomorrow night for the rest of the week. So we'll see.

 

Thank you for the kind offer langers2k.

I am at the bottom of a steep learning curve on DPF's having recently bought a 2015 2.0TDi Yeti, its in another country from where I am so I cant go out and play with it and when I was there i was busy with repairs (insurance write off).

 

I did have a play with VCDS and all the measuring blocks, blew my mind how many there were! Anyway I'm sure that it gave the KM's since last regen as the kilometrage that the vehicle has done, - 85K miles = 136K kms. Does this mean it has never done a regen, or has only done passive regens?

 

Is that a good or a bad thing? sounds like it might have done mainly long motorway journeys which I guess is good.

 

I did see the soot level but cant recall if it was calculated or measured, it seemed very low, less than 10 or 20 grammes but if its foutu at 45g it doesnt seem so low now.

 

The VIN checkeing site says that the emissions mod has been done and I have just read that a regen will be done every 250 miles, is that a passive or active one? Surely an active one plays hell with the fuel economy?

 

What should I be checking next time I am there with VCDS? If possible also what measuring blocks and what controller as there are just so many compared to what I am used to.

 

Thanks a lot.

@J.R. - everything DPF related will be under 01 - Engine.

 

The important figures in my opinion are soot calculated, soot measured and oil ash. All three should be found under the measuring blocks and given the number, using the search function is by far the easiest way to find them ;)

 

Soot measured and calculated tend to be very different. I believe this is because calculated doesn't take into account passive regeneration's whilst measured does. Both should be below 24g and will probably less than 18g. Oil ash volume valves will depend what units it's measured in.

 

It's an active regeneration that's done every X miles, it won't help fuel economy but I doubt it effects the average massively as it's only small amounts of diesel that are being used for short periods. After 85k miles, it will have done many, many active regeneration's...

 

As for the 'kilometers since last regeneration' measuring block, check the units! At least my ECU shows the distance in meters despite the title saying KM so values of both 85000 (85km) and 136000 (136km) are perfectly fine. Looking at the logs I collected for the graph above, it hit 585701 (585km) before resetting to 0.

There's no such thing as 'a' passive regen. Passive regeneration, if/when it does happen is a continuous process of soot combustion that will continue for as long as conditions are hot enough, and rate of burn > rate of arrival of new soot. The only way you will know if the soot loading is decreasing in such a manner is if it is logged continuously with VCDS or similar.

Thanks to you both, more learning required for me just to stand still let alone get ahead of the game!

 

The search function that you speak of Langers is that within VCDS?

 

No surprise to learn about the units, I should have expected something stupid like that from the programmers.

17 minutes ago, J.R. said:

The search function that you speak of Langers is that within VCDS?

 

Yup, at least for modules that support advanced measuring blocks. You can see it search box in the second image on this page: https://www.ross-tech.com/vcds/tour/adv-meas-blocks.php

On 30/09/2019 at 22:01, BushcraftChris said:

I thought I'd start a new topic as both these issues seem to be linked together on my car, which I've had for 18 months. (115k 2012 Octavia Scout Mk2 2.0 tdi).

 

Symptoms:

Cold temperatures and/or dry weather (-5 to +5 DegC): Car sometimes decides to increase revs from 750 ish to 950-1000rpm. Also the area around the engine bay starts to really smell of diesel. (Aircon not turned on). Turning the engine off will sometimes clear the fault.

Warm temperatures & wet weather (+5 to +15 DegC): Ditto. Note, it doesn't seem to happen above 15 DegC air temp.

 

Having done lots of reading tonight, & taking these symptoms into consideration, I'm suspecting that there may be some water/moisture shorting something out.

• Possibly one/both of the engine temp sensors,

• Possibly the radiator fan switch temperature sensor,

• Possibly the fan control module itself.

• Might even be a loose connection, or

• A rusty earth connection or 11.

 

Has anyone had the same problem before and if so which of the above was it? With the approaching hurricane Lorenzo and the rather wet conditions, I'm not going to be investigating anything until the weekend at the earliest, so a "starter for 10" would be appreciated.

 

Thanks

Hi, I have the same problem and changed all the parts u said above.

No luck, have you sorted out your car yet 

Thanks 

Hi. I suspect that it's to do with the DPF as these are all things the car does while doing an auto burn. Sadly though, mine has continued to do this. Further research indicates that the DPF will ultimately get full and require manual cleaning using solvents, or a complete replacement.

 

Things to look forward to. 😥

I see that I have previosly responded to this thread with some weird text...

 

I've noticed that my car increases revs to ~1k in 3 cases:

 

1) hot weather (with AC on - needs extra power for it). If you turn AC off, the revs should decrease (not immediately, though);

2) cold weather - while engine is cold, it's normal thing. Usually goes to normal after some warming up.

3) DPF regeneration on.

 

So, in hot weather try to avoid AC in a test drive and watch revs then. In cold weather after certain warm up revs should be in the normal range. DPF thing - well, until it's finished.

 

At least for my car these high revs are common thing in certain situations.

 

 

As Jevpls above PLUS battery needs recharging for multiple reasons, including a battery nearing end of life.