Rough idle when cold

chill200sx

New Member
I have recently purchased a LWB t6.1 highline 150 manual, it’s covered just over 100k on a 2020 plate as a commercial vehicle. Unfortunately the history is patchy but I took a chance on it as it was within my limited budget.

I noticed the following day after purchase on the first start up of the day it runs very rough, idle blips up and down and it sounds like it’s only firing on 3 cylinders. I thought it might just be because it needed a good run but unfortunately not, after a few good runs it’s no better if anything possibly worse.

It drives spot on pulls well and once driven only to the end of the street the idle is fine, I’ve done a lot of reading around and can’t find anything specific to this. The only thing I’ve seen that I have slight concern about is the dual mass flywheel being mentioned as a possible cause. My concern for this is because the previous owner said he had the clutch done about 6 month ago, I’m just thinking it could have been a poor job or misdiagnosed flywheel issue. Also on a couple of occasions it’s popped out of first when I’ve been setting of from the lights, I just assumed this was because I wasn’t used to the vehicle and hadn’t fully engaged the gear but now I’m wondering?

Any help would be greatly appreciated, I’m based in Leeds so any advice on a good local place to take it would be useful too, ideally not one of the places that seem to think you have money to burn because you own a transporter.

Thanks.
 
I'd suggest the first thing to do is to get something capable of reading the fault codes and post those.
I have used a cheap obd reader when I bought it but nothing showed. What else would you suggest to get a better read? There are no lights on dash etc and when I’ve read about rough idle problems most are suggesting nothing is showing?
Cheers.
 
Carista/OBD11/VCDS are the generally recommended VAG specific tools - as you've found the generic ones rarely work well.

Lots of conversations of pros and cons such as


If you're not sure get a basic Carista - they're cheap and the first month subscription is free. If it works for you then just pay for the month when you need it. If you never use it again or you decide you want something more extensive you've not spent much.

You don't need the newer version if you only want VAG use.
 
Any white smoke on start-up after sitting overnight? It could be a glow pug, a coolant leak from the EGR cooler into the inlet, or a leaking intercooler into the inlet
 
Didn’t notice any white smoke although I was more focussed on taking a video? Any clues on how to post it? I tried the video attachment but it just says oops ran into some problems. It’s 3.30 long is it too long?
 
Didn’t notice any white smoke although I was more focussed on taking a video? Any clues on how to post it? I tried the video attachment but it just says oops ran into some problems. It’s 3.30 long is it too long?
You can only attach images directly. For video or other media upload it to a hosting site like YouTube SoundCloud Vimeo and then use the embed media link.
 
sounds like it’s only firing on 3 cylinders.
Yes, sounds like it's not running on all four cylinder.

The only thing I’ve seen that I have slight concern about is the dual mass flywheel being mentioned as a possible cause.
Perhaps not the cause but rather a consequence. I believe the metallic "clunks" are from flywheel pendulums hitting their limiters - because of uneven running.

What the engine code - something like CXF-, CXH-, DNA-? It's on the sticker below
1718087569334.png

Somewhat similar symptoms here -
 
Mine was lumpy at low revs/cold. Diagnosed by garage and have just had flywheel replaced.
 
Engine number is CXH 275 053

I’m really hoping it’s nothing too serious, literally runs rough for 30/60 seconds on first start up of the day and then is fine after that?¯\_(ツ)_/¯
Yes, sounds like it's not running on all four cylinder.


Perhaps not the cause but rather a consequence. I believe the metallic "clunks" are from flywheel pendulums hitting their limiters - because of uneven running.

What the engine code - something like CXF-, CXH-, DNA-? It's on the sticker below
View attachment 245516

Somewhat similar symptoms here -
 
Only other thing I would say is it seems to get up to temp very quick, quicker than my Passat, but then just sits at 90.
 
The temperature display is stabilised at 90 for the normal operating range - presumably to stop folks worrying too much but to draw attention if it's really wrong.

If you have the option to show oil temperature that's a more raw figure.
 
Interesting that they state that the oil temperature guage is stabilised too - on my 6.1 the display of oil temperature under the options of the digital dash is definitely not stabilised as I use that as a more "true" temperature when I deliberately want to work the engine a bit harder...
 
I can’t see a failed DMF causing this rough running, it’s a misfire, if there is any DMF noise it’s as @mmi stated in post #10.
My advice is not to run the engine at all in this condition, I don’t see much improvement over the length of the posted video. If an injector is delivering fuel without complete combustion it is going to wash the cylinder bore, dilute the engine oil and destroy the DPF. Not a chance worth taking.
It maybe a slightly bent connecting rod caused by hydrolocking due to a leaking EGR cooler, this is a known issue.
My advice is to read the fault codes, monitor the coolant level / reservoir pressure and preferably get a Miller oil analysis to determine the state of engine wear and fuel dilution.
 
  • Like
Reactions: mmi
it seems to get up to temp very quick,
Normally can take up to 15 minutes. However, if it's doing DPF regeneration then it's very quick.

In the video the coolant bottle seems to be quite full?

1718300049883.png
 
Normally can take up to 15 minutes. However, if it's doing DPF regeneration then it's very quick.

In the video the coolant bottle seems to be quite full?

View attachment 245933
I questioned that when I bought it and he said his mechanic said the seam of the bottle is the max line, I did t think this was the case so googled it and the information is inconclusive, as in people arguing the seam is the max and other people saying the second line is the max?
 
I had a clutch/flywheel replacement last week, at 127000
I asked the garage to check the engine mounts while under there, as mine was so rough from start up.
It did sound like it was running on three, it was so rough.
Now that has been done, it runs like brand new. An unbelieveable difference.
It also was making a very strange noise, especially between 60-70 in 6th, which I had thought could possibly be a turbo, but this too has now gone.
No judder in reverse from cold either, which is nice.
 
Back
Top