My vRS suffered a mis-fire, then dropped to running on 3 cylinders.

 

Spark plug 3 was found to be black (carbon or burned on oil?) - see pic.  Spark plug 2 was slightly fouled, 1 and 4 were OK.

The plugs were replaced (coil packs have already been replaced), but after 500 miles or so, the plug is turning black again.

 

Other symptoms which may have a bearing - slightly high oil consumption, and slight smoking on full throttle.  Coil packs 2 and 3 have a small amount of green goo on them.

 

Could this be either the PCV on its way out, or possibly the valve cover gasket?  Or am I looking at something more sinister (and expensive)?

 

Thanks in advance

You don't mention the mileage the car has covered. I know these engines suffer from excessive carbon build up on the intake valves so that might be the problem. It is an issue inside the cylinder itself ( too rich ) so an external gasket is unlikely to be the cause. The pcv may cause it i suppose and those are a known weak point a rough idle might give a clue. Like anything, start at the easy stuff. If the car has covered around 50k plus it maybe sticking valves. Hope this helps.

Sorry, should have said - the mileage is 60,000.

 

Is it likely that a carbon build up could affect one cylinder more than another?

Sorry, should have said - the mileage is 60,000.

Is it likely that a carbon build up could affect one cylinder more than another?

I'm not sure but it is likely all could be coked up to a point but 1 cylinder bad enough to cause running issues. I would look at the pcv first though as it's easier and cheaper to sort. Do you have an engine check light on?

The engine check light came on during the initial misfire

I had:

001089 - EVAP Emission Control Sys
               P0441 - 000 - Incorrect Flow - Intermittent

 

and

000771 - Cylinder 3
               P0303 - 000 - Misfire Detected
and

004874 - Cylinder Disabling
               P130A - 000 -  - Intermittent

 

 

I assume that the EVAP and cylinder disabling are symptoms of the Misfore, rather than actual problems?

I read elsewhere that the newer TSi engines don't have a tradtional valve gasket - instead it uses 'green goo'.  I had some small amount of green goo on the coil packs.  Is this normal?

 

I'll strip the PCV off and have a look at it, are any problems likely to be detected visually (split seals / diaphragms etc)?

I know this is an old post but did you ever get to the bottom of the problem, my car as been doing the exact same thing for months, changing coil packs and plugs don't help the problem comes back