Misfiring when started after being sat for a few hours

[trevorwilson]

I have a 2018 1.6 TDI SE DSG and it has run perfectly it's whole life (45k miles). I had it serviced recently and ever since then it has run badly for a minute or two when it is started after it has been left for a few hours. When I start the engine after it has been idle for approx. 12 hours or more it starts just fine. Then, after a few seconds it seems to misfire (I know that's probably not the right term but you can put me right ) and the engine runs very rough for about a minute, almost stalling at times. Revving the engine a little doesn't really help. As soon as I have driven for a couple of minutes the engine runs normally again. Did a 500 mile drive yesterday and it all appeared to run as normal once I had got past the initial jittery phase in the morning.

1. It seems to be related more to the length of time the car has been sat idle rather than the temperature of the engine - after four hours yesterday the engine was completely cold but it started and ran perfectly fine, but then when I left it overnight the problems resumed this morning.
2. The garage think it is dirty injectors. I have just run through a tank of fuel with Forte Injector Cleaner but the problem is getting worse, not better. Also, why would that start just after a service?
3. The garage said there were no error codes relating to the engine when they checked it.

I am wondering whether there is air / water accumulating somewhere when it is sat long enough which is then flushed out of the fuel system after a minute or two? I really have no idea - has anybody any advice? The garage now want to hook the car up to a machine that cleans the injectors but I am worried I am throwing money at it when the problem seems quite speculative.

 

[kyLman]

You mentioned getting it serviced recently, what did that include? Did they throw in spark plugs incorrectly gapped? Wrong mfg'er/ style? I am leaning towards coil packs, spark plugs, etc.

 

[trevorwilson]

You mentioned getting it serviced recently, what did that include? Did they throw in spark plugs incorrectly gapped? Wrong mfg'er/ style? I am leaning towards coil packs, spark plugs, etc.

Thanks for taking the time to reply! The car is a diesel though, so it doesn't have spark plugs.

 

[kyLman]

Thanks for taking the time to reply! The car is a diesel though, so it doesn't have spark plugs.

Doh - I missed that when speed reading. Sorry, I am not familiar enough with diesels.

 

[jimlloyd40]

Sounds fuel related either injectors or pump. Don't know anything about the PCV system on a diesel. I would demand that they fix it at their cost since it happened right after they serviced it. List exactly what they did when they serviced it. Also don't know anything about the fuel filters on a diesel. Or the regeneration thing.