A3 1.6 Cold Start Stalling

[33peterh33]

Hi all,

I have a weird issue with my A3 that I am struggling to get on top of. I have scanned with diagnostics and only a static fault is coming back with the MAF however I don't think this is causing the issue.

Basically when it is cold in the morning and I turn the engine on it will idle for about 3-5 seconds then the revs will become irratic before eventually stalling. It does this about 5 to 10 times before it idles fine, however once you are moving the car hesitates sometimes and loses power. Nothing is showing on the dash. Once the car has warmed up startup is pretty much straight away and power appears to be fine. Driving on the motorway the car feels fine and smooth even at 70+mph.

It is very simular to this: 

Its with the garage but they can't find anything obvious with it but they managed to replace the cold start issue. Could it be the EGR dispite no codes being logged or perhaps the glow plug relay?

[Magnet]

Hello Peter,

Sorry to hear of your problem. There is a common belief that fault codes are king, and if there isn't a code there isn't a problem. I must admit that code reading is not my sphere of experience, and I'm sure that it is indeed an essential tool in problem solving, but I have some concerns about the possibility of cause-and-effect being ignored when the diagnostics show up a fault on one component and that fault may be linked to a problem with another component. Anyway, opinions over! 

My hopefully postive path from here would be to ask if there was any associated smoke when the idle is erratic/ after cut out and restart? 

Dependent on your answer to this I might suggest a trip to a local diesel specialist who will probably test the injectors for you, since it is possible that this is where the answer lies. Take it the glow plugs have been checked. 

Kind regards, 

Gareth. 

[33peterh33]

Thanks for you reply.

There is white smoke in the morning when it tries to idle but then stall if it is cold. Aprrently previous owner has had two glow plugs cleaned or replaced as they where dirty. I did hear about the glow plug relay being a possible candidate to the issue.

If the current Indy garage can't find the issue I will try a diesel specialist next to see if the injectors are at fault.

 

Thanks,

Peter

[Magnet]

Hello Peter,

Interesting. Not sure why the previous owner would have changed just two glow plugs - a bit like changing 2 spark plugs rather than the set. 

If the two original glow plugs test OK then my money would be on injectors, and it would then be worth having a leak-back test done on all four. 

If it were me, I would by pass an independent in favour of goung straight to a local diesel specialist, particularly since normal practice is for the garage who you may take it to would probably drive it around to the diesel people and charge you for secondhand assessment, plus a bit understandably added on for their involvement.

Kind regards,

Gareth.