Lumpy idle. White spots on top of pistons?

steve_b9 · 12-09-2019, 03:42 PM

I've been chasing a lumpy idle for a while now.
It'll sort of rock the car gently on idle. And have the od splutter. I don't have access to ista.
Plugs and coils are all new.
About a week ago I started it up on a very cold day and instantly got half engine light and very rough running.
Checked the codes. Had combustion misfire cyl 3. And cyl 6.
Today I pulled the spark plugs to check for leaking injectors.
None were damp and all were clean. But the engine was still warm from driving to the workshop.
Looking down the spark plug holes I noticed white spots on top of the piston directly below the injector. But only on cyl 3 and cyl 6.
Does anyone know if this is caused by leaking injectors?
Any help would be appreciated

weehe126 · 12-09-2019, 05:17 PM

Looking with your eye or a scope?

steve_b9 · 12-10-2019, 12:44 PM

Looking with my eye. Thinking about it the white spot is directly below the spark plug not the injector.
Regardless of where it is. Would a white spot on the top of the piston be a sign of a very hot burn. Like there is too much fuel?

weehe126 · 12-10-2019, 01:01 PM

It's probably the only spot light is getting in. You would need a scope to determine anything useful.

12-09-2019, 03:42 PM	#1
steve_b9 New Member 0 Rep 17 Posts Drives: bmw 335i se lci Join Date: Mar 2019 Location: gloucester uk iTrader: (0)	Lumpy idle. White spots on top of pistons? I've been chasing a lumpy idle for a while now. It'll sort of rock the car gently on idle. And have the od splutter. I don't have access to ista. Plugs and coils are all new. About a week ago I started it up on a very cold day and instantly got half engine light and very rough running. Checked the codes. Had combustion misfire cyl 3. And cyl 6. Today I pulled the spark plugs to check for leaking injectors. None were damp and all were clean. But the engine was still warm from driving to the workshop. Looking down the spark plug holes I noticed white spots on top of the piston directly below the injector. But only on cyl 3 and cyl 6. Does anyone know if this is caused by leaking injectors? Any help would be appreciated
	Appreciate 0 Tweet Quote

12-09-2019, 05:17 PM	#2
weehe126 Brigadier General 1161 Rep 3,189 Posts Drives: 2017 340i Join Date: Apr 2014 Location: San Antonio iTrader: (2)	Looking with your eye or a scope?
	Appreciate 0 Quote

12-10-2019, 12:44 PM	#3
steve_b9 New Member 0 Rep 17 Posts Drives: bmw 335i se lci Join Date: Mar 2019 Location: gloucester uk iTrader: (0)	Looking with my eye. Thinking about it the white spot is directly below the spark plug not the injector. Regardless of where it is. Would a white spot on the top of the piston be a sign of a very hot burn. Like there is too much fuel?
	Appreciate 0 Quote

12-10-2019, 01:01 PM	#4
weehe126 Brigadier General 1161 Rep 3,189 Posts Drives: 2017 340i Join Date: Apr 2014 Location: San Antonio iTrader: (2)	It's probably the only spot light is getting in. You would need a scope to determine anything useful.
	Appreciate 0 Quote