Technical Smoke on start up

[chilly500]

Every now and again my 1.2 belches smoke on start up. It's a grey colour not blue like burning oil.
When it does it the engine won't rev cleanly and sometimes dies if not blipped. Can anybody tell me what causes it?

 

[griff74]

If it's not blue and the car runs rough I would say it's the mixture, maybe over fuelling when starting, does it just do it when cold or when it's warmed up?

 

[chilly500]

Just seems to do it from cold, usually when it's been stood a while.

 

[jrkitching]

It's a common issue - nothing to worry about unless it becomes excessive.

IIRC the fuel rail doesn't depressurise on switchoff so a small amount of unburnt fuel may be leaking past the injectors when the car is left standing.

Also the initial mixture for starting will be very rich and if a cylinder doesn't pick up immediately then that will also cause unburnt fuel to pass into the exhaust system & give a smoky start.

Ever seen those big radials on old airplanes start up & pondered on the amount of spluttering, smoke & sometimes even flames as the cylinders lazily start firing in their own time?

If the spark plugs are worn, this will make the problem worse.

From personal experience, fitting new plugs will usually improve or fix this, and the issue is noticeably less if you fit iridiums.

 

[chilly500]

Thanks guys. It's had new plugs fairly recently. As long as I know it's not a fault I can live with it

 

[Piccolo Nero e Bella]

Also the initial mixture for starting will be very rich and if a cylinder doesn't pick up immediately then that will also cause unburnt fuel to pass into the exhaust system & give a smoky start.

They tell you not to push-start the car because this will allow raw fuel through to the catcon and damage it so how likely is this to be an issue for the converter?

"Ever seen those big radials on old airplanes start up & pondered on the amount of spluttering, smoke & sometimes even flames as the cylinders lazily start firing in their own time?"

Not just the radials - have you seen video of the Griffons starting on a Shackleton...

 

[MrDerv]

Ours did this prior to a software update last month, however, i started it up yesterday, and it stuttered like hell and belched blue and grey smoke. It only has 5900 miles on and just under a year old.

I'll be making a phonecall to the service department again this week :bang: