Rough idle - sometimes....

[Gary W]

Hello gents. Got a 3.0TDi A6 Avant - 2012. 135k on the clock. 

Recently started getting a rough idle - but only for about 30 seconds or so, then it settles down. Also a slight juddering when accelerating, but only at low revs then it's fine. Sometimes the rough idle produces rough engine noise - but then it's fine after 30 seconds or so and is fine when I'm driving. 

Any suggestions? VCDS says glowplug and cylinder 1 - no other faults. Going to clean the MAF. Still rough idle if I remove the MAF sensor. Hoses seem.ok and not split.

Not really much of a mechanic - just trying what people tell me and seeing what I can figure out via YouTube. 

Any suggestions welcome 👍🏻

[Stevey Y]

6 minutes ago, Gary W said:

Hello gents. Got a 3.0TDi A6 Avant - 2012. 135k on the clock. 

Recently started getting a rough idle - but only for about 30 seconds or so, then it settles down. Also a slight juddering when accelerating, but only at low revs then it's fine. Sometimes the rough idle produces rough engine noise - but then it's fine after 30 seconds or so and is fine when I'm driving. 

Any suggestions? VCDS says glowplug and cylinder 1 - no other faults. Going to clean the MAF. Still rough idle if I remove the MAF sensor. Hoses seem.ok and not split.

Not really much of a mechanic - just trying what people tell me and seeing what I can figure out via YouTube. 

Any suggestions welcome 👍🏻

Hi could well be a glow plug problem but I would change the whole set, not worth playing chase the ace when the others start to fail, nearly all the diesels are post injection engines which rely heavily on glowplugs for starting and the start of DPF regeneration they come on to heat the extra fuel that burns off the ash in the DPF, Also one of the plugs is a knock sensor as well as a glowplug.

Steve.

[Gary W]

Nice one, cheers Steve. As I said - I'm not really much of a mechanic - but assumed that the glowplugs wouldn't cause me issues in the warmer weather. I'll look into getting them replaced 👍🏻

[Gary W]

Just as an update - thought I’d let you guys know what’s been going on…

Imagine the worst case scenario - then x10! 
 

Booked the car in to have the glow plugs replaced. Couple of days before the glow plugs were due to be replaced - car cut out. It was hard starting but wouldn’t start. Recovery came out and sprayed a bit of ‘cold start’ in the air intake. Car started for about 1 second then stopped. Recovery say it’s a knackered injector, not glow plugs. 
 

Have car recovered to garage.  Garage say fuel pressure is fine from tank to engine, but low to injectors. They change fuel filter but this makes no difference. They say the high pressure pump could be knackered and it needs to go somewhere else as they won’t touch it. 
 

Booked it into a diesel injector / fuel pump specialist to be looked at next week. 
 

They warned me that if the high pressure pump is knackered, it’s likely that all my injectors will also need replacing 😭

Update to follow….

[neko]

Hi Gary, any update on your predicament? Have similar issue myself 

[Gary W]

You don’t want to know…

1 new injector and 5 x reconditioned injectors = £2400.

On the plus side - it was like driving a new car after it was done. 
 

Until….

2 weeks later - coolant leak. Long story short - £2020. 
 

Total bill for 1 new injector, 5 reconditioned injectors, dealing with coolant leak = £4420. 
 

Now have that dilemma of: do I get get rid, do I keep, what’s next…

Not what you wanted to hear - sorry!

Edited October 6 by Gary W
Typo

[neko]

Thanks for the reply (good or bad 🤣) so was it just the injectors? Or did the hpfp fail and had to be replaced and ruin them? 

[Gary W]

One injector was completely knackered and 3 were not in a good way. I thought it would be best to have a new injector for the knackered one and have all of the other 5 reconditioned. 
 

The pump was fine - luckily.