Hi,

 

I have a 2018 Octavia 1.6D DSG with 185k km on the clock. The engine idle is rough when the engine is cold. I usually have to wait 1 minute for it to start working normally. Then it's fine for the day. It is worse if the outside temperature is low. My mechanic initially recommended using the VW injector cleaner. That did not help.

He said he does not really know what is wrong and wants to replace all injectors which he's quoted at €1300.

Is this the only option? Do all injectors have to be changed at once or can only the faulty one be replaced? I would like to avoid such a big repair bill, of course.

4 hours ago, AndyTheDude said:

He said he does not really know what is wrong and wants to replace all injectors which he's quoted at €1300.

Is this the only option?

Change fitter for one who is competent to use diagnostic software to identify which injector(s) are faulty.

Edited 12 December, 20241 yr by Paws4Thot

Rough idle when cold could easily be due to worn out glow plugs, or glow plug circuit not functioning correctly. Compression issues, eg due to partly worn out rings or cracked pistons, also manifest themselves more often from cold. Could be also other reasons like faulty sensors.

I'd replace injectors last, not first.

What I would do is first a VCDS/OBD2 code check, often there is an error code pointing to why the engine is unhapy. 

If there are no error codes then glow plug test, or if glow plugs never replaced then glow plug replacement together with compression test, first on hot engine (glow plugs need to be taken out on hot engine anyway), then compression test again on cold engine. Compression test tool is cheap, screws in place of a glow plug.

The fitter is charging a lot for labour. The plugs themselves can be got for less than £250 for the full set incl the 'special' one.

Thanks for the replies, I'll get another mechanic to have a look at my car. He didn't even mentioned glow plugs or error codes, he just wanted to go straight for the injectors.

2 hours ago, AndyTheDude said:

glow plugs

My bad. Mis-read your earlier post clearly stating injectors.

Does glow plugs continue to work on working engine too? Don't know- that's why it's interesting to know.

1st replacement of glow plugs on my friend's Golf7 (same engine family) was around 230k km.

Other Octy3 I know (210k km) still have old original glow plugs.

Am pointing to fact that at Andy's Octy at 185k km they still can be ok. Can be...

Edited 13 December, 20241 yr by indars
typing error

OK is a relative term. I used to have Mk1 Superb 2.5TDI V6 where glow plugs did not show open circuit, but gradually reduced performance until cold start problems started appearing, I think around 8 years time or so. The resistance has increased by a factor of 2x, so they were heating only half as well compared to when they were new.  Replaced the lot (6 of them), have not had a problem afterwards until the end of car at ~350kkm / 219k miles. 

 

On other cars, 4-cyl TDIs, I usually had one glow plug blown and at this point replaced the lot. I always replace with NGK ones that glow hotter, perhaps that's why so far, I did not have to replace them again, even if they wear out a bit, they're still hot enough.

 

Glow plugs do work for quite a while after engine start, this is both for smooth running when cold and for emissions reasons.

Edited 13 December, 20241 yr by dieselV6

We are missing a scan.  Is the OP able to get a scan done of the car, because rough running like that will cause the car to trigger a code - showing the problem.