RPM Fluctuation when Engine Cold and Electrical Consumers On (Golf MK6 1.6 TDI)

[Airbus]

Hi All,


Perhaps someone can assist. Since I have had it my car, a Golf MK6 2012 Model 1.6TDI (engine CAYC) has suffered from a slight but regular fluctuation in the RPM between 740-820rpm (as per VCDS) which you can feel through the steering wheel. Pre-Requisites for this to occur are engine cold and Electrical Consumers On (i.e rear demister, headlights, Heater on etc). It always disappears as soon as the engine is warmed up (10 mins or so). The fluctuation is regular, like every couple of seconds or so only when the above requirements are met. I am noticing it a lot more since the weather has got colder in the UK and I use more consumers at startup.


The EGR Valve was changed early this year so this has been ruled out. Unfortunately I don't know whether the issue was apparent before then as that was under another owner.
The Injector deviation have been checked on all 4 cylinders and I can't see anything wrong there either (1mg max deviation on any one).
Battery Voltage shows between 12.3-12.6V at rest and alternator shows charging well at 14.8V when on.


There are no fault codes present in VCDS


Has anyone experienced such an issue as I am losing things to check?

Thanks.

[Crasher]

The CAYC engine is terrible for running problems, if the EGR valve was non genuine VW this can often be the problem. Has the emissions recal be done? This often makes them run badly and there are reflashes on the VAG system for some models plus smooth running help. The injectors on the CAYC are a bad joke, they often need all four and pattern or recon units are rubbish so it’s new genuine parts at £2500 fitted.

[Airbus]

The CAYC engine is terrible for running problems, if the EGR valve was non genuine VW this can often be the problem. Has the emissions recal be done? This often makes them run badly and there are reflashes on the VAG system for some models plus smooth running help. The injectors on the CAYC are a bad joke, they often need all four and pattern or recon units are rubbish so it’s new genuine parts at £2500 fitted.

Hi Crasher,

Thanks for your reply. The EGR Valve was changed at a VW Main Dealer early this year. Unfortunately the Emissions recall was done in 2017, the ECU has been updated to 9982 as a result. I asked the dealer whether there were any subsequent updates available for the CAYC engine and they said 'not to their knowledge'. Not the most helpful people I have been contemplating having some form of software roll back done at an indy since VW flatly refuse to try this. Just not sure this is the best way because the actual running once warm is perfectly fine. Would you happen to know of any reflashes around for the CAYC, past version 9982. Its hard to battle with VW when they flatly refuse to acknowledge an issue, the particular dealer seemed to just look for fault codes and not the actual physical problem.

I checked the injector deviations and they seem fine in VCDS (less than 1mg on all 4), and the issue is only directly linked to the engine being cold and electrical consumers on. I have had injector problems on a previous 1.6TDI CAYC, and the revs fluctuated randomly and sporadically. This is regular, like a pulsing rev up and down every 2 seconds or so (740/820rpm). If I turn off all electrical consumers, the problem tends to go away even if the engine is cold. I am leaning towards the battery or the alternator but I really don't have any substance to this argument as the voltage seems fine.....just the battery is original (6 years old).

Thanks again for taking the time to reply.