I've a 2014 2.0tdi with 300,000km on the clock. Recently when cold the car jerks & hesitates in mostly 1st and 2nd gear under acceleration. By 3rd gear its fine, and once the engine is running for a few minutes its fine. My mechanic is convinced its glow plug but I'm not so sure since the car starts fine.

Any ideas from anyone else?

It's very strange when the issue goes away so quickly once running.

No fault codes? Will it start good and will it idle good at cold?

Nope, no codes. Starts first turn of the key with no hesitation so its not like a worn or aging glow plug. Idles fine (no stuttering). Its just when pulling away in first, to second (this is the worst), then to 3rd, by the time I'm in 4th its fine. And then its gone entirely when running for a few minutes.

4 hours ago, JustAFlabbyPanda said:

Nope, no codes. Starts first turn of the key with no hesitation so its not like a worn or aging glow plug. Idles fine (no stuttering). Its just when pulling away in first, to second (this is the worst), then to 3rd, by the time I'm in 4th its fine. And then its gone entirely when running for a few minutes.

How soon you start driving after cold start? If you wait and engine warms up little bit does it hesitate? Will it rev okay on idle?

Revs fine. If I left it idle for a few minutes (3 to 5) it's less noticeable. It's worse when I start the engine and immediately pull off from cold (and the ambient temp is 10c or less). As I said within a few mins of driving it's gone completely even when coming to a stop again.

Are you sure there are no codes? faulty glow-plugs and faulty injectors do generate fault codes though. 2 years ago I had the same issue. With a cold engine with outside temperatures dropping, the engine need a bit more fuel. It appeared the injectors never had been cleaned so they got contaminated with dirt. So I replaced them with new injectors. 300.000 km is a respectable number so it may be wise to replace them as well. However, you could first try to clean them by adding injector cleaner to your diesel tank and fill it up with diesel as well. very often those manufacturers advise, for curative reasons, to add 2 quantities initially. For preventive maintenance the advise 1 quantity every 10k. km.
If this doesn´t help then replace the injectors.

Yes 100% no codes. I was going to run injector cleaner through them alright but as I say the fact that the issue goes away makes me reluctant to load up the parts canon.

Manual or DSG?

Manual.

That eliminates the possibility of a DSG fault causing jerkiness that might feel like an engine hesitation.

I take your point about not employing the parts cannon, but I think I would be throwing a bottle of complete fuel system treatment in and going for a long drive. For a tenner I think it would be worth a punt.

So this morning as a test I started and left immediately but was much more delicate with acceleration and it seems fine. It was 10c outside.

Tomorrow I'm going to let it idle for 5 mins and then drive it like I usually do and see what happens.

I've used this method before to clean injectors and will repeat at the weekend and see what its like. https://www.youtube.com/watch?v=_1rCgFPfEkQ

9 hours ago, JustAFlabbyPanda said:

Tomorrow I'm going to let it idle for 5 mins and then drive it like I usually do and see what happens.

it would be interesting to see the result of you efforts. Btw, what diagnostic tools have been used to scan for faults?

Well my aux belt left the building on the way home from work yesterday so I need to replace that first this weekend before I can do more testing.

I've got a bluetooth dongle and I use the Car Scanner app on the play store. It has profiles for a wide range of cars and hasn't failed me as yet. For reading & clearing codes its fine. My buddy has a snap-on commercial unit that we've done comparisons with. Mine lacks the ability to actuate devices/relays/etc but apart from that its ok.

I am afraid, Car Scanner is not capable providing you with detailed information. Unfortunately I am not familiar with the Snap-On scanner. Personally I would recommend using OBDeleven or VCDS for proper diagnostics.

I had obdeleven before and returned it. I found it worse than car scanner tbh.

I've avoided vcds as I've no need for coding etc and the cost makes it prohibitive.

I got the belt replaced at the weekend and I'm off today so tomorrow I'll do a test from cold after idling it for five minutes.

Car scanner is good. If you manage to get connection with app and bt reader, allmost all app's are fine for basic things like temp or most common fault codes.

22 hours ago, Karpov said:

Car scanner is good. If you manage to get connection with app and bt reader, allmost all app's are fine for basic things like temp or most common fault codes.

I disagree here as Car Scanner is making use of the ELM 327 dongle and, yes, it may return some basic fault messages but in a more generic way. Both OBDeleven and VCDS will give you indepth fault messages which can never be achieved with Car Scanner. Personally I use OBDeleven and Car Scanner

OK lets not get hung up on the scanner, there are no codes even with a mechanics pro scanner tool.

Let the car idle this morning (5 degrees) for at least 5 minutes and had no issues at all. Not really sure what that points to now except that once its warm it goes away.

To me that's not really a solution just a workaround.

Was it the coolant that was warm in 5 minutes. Was it near 90*oC or indicating that? The oil was not even at 50*oC was it after 5 minutes idling?

It didn't even occur to me to check, school run, I'll confirm tomorrow.

5min idle at cold engine is maximum 40c coolant if there is ot freeze outside.

I once had 2003 1.9pd where i changed fuel filter with those o-rings what were on fuel filter bracket. It was also jerky at cold but it was jerky at idle also.

Can you check all fittings, hoses etc which are on fuel system?

Have you tried 1-3minute idle?

I was tempted to swap the fuel filter as its an easy job. Will check the connectors but I didnt notice any leaks etc when I did the belt at the weekend.

I've only tested driving away immediately and 5 mins

Was idling for around 10 mins this morning, outside temp was 5c, engine coolant was 46c and oil temp was 51c. No issues when setting off.

Will check with a 1min idle tomorrow and see how it goes.

Waiting on injector cleaner to be delivered.

Thats weird you have oil temp higher than coolant temp. Usuyally when my coolant reaches 70c then oil temp is 50c.

Was idling for a solid 10 mins this morning but the ambient temp was 1.5c. Coolant and Oil were both 47c and it was jerky again. So I've no idea really. Not sure there is any benefit to idling it when it takes so long to get hot.

Still waiting on injector cleaner.