Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
there is no visible smoke while running, only on some startup light smoke. new plug with 0 miles never driven is already black. only from stating it and diagnosis running it. when warmed up misfire on that cylinder . pulled out the exhaust manifold and it was shiny black wet with some fluid droplets the other cylinders were dry black.
no overheating no loss of fluid. im guess the droplets you see in the video link could be slight water coolant. however it doesnt smell like coolant. its possible it could be coolant not sure. it happens when warmed up assuming when thermo is open allowing flow.
all test done not sure why the ecu is shutting down the injector on that cylinder .
I have seen a similar issue on another vehicle I worked on with a blown head but it was noticeable due to the piston top being clean and seeing coolant out the exhaust manifold under leakdown test.
however on this vehicle the piston is shiny black wet. unless there is a very small amount of coolant getting in.
haven't even driven the vehicle since the plug was replaced. the vehicle came in with ignition parts and one new injector so im just backtracking checking things while diagnosing this issue.
Coolant leaking into the cylinder like that will just look and smell like water. Fuel will smell like fuel and oil will feel like oil on your fingers. I doubt you will notice overheating or coolant loss if it’s a small leak. It doesn’t take much to wet the plug down and cause a miss
I thought compression must be the issue but all the cylinders are about 180psi. leak down test doesnt show any major leakage, similar as next cylinder to it. im guessing lifter issue. I connected a vacuum gauge and when its not misfiring before fully warmed up its in the green indicator when it starts misfiring it drops slighly out of the green indicator range.
boxster
there is good spark from spark tester . I see that the ecu stops firing the fuel injector it start to misfire.
vehicle came in from 2 different shops with new plugs coil and injector however the misfire stays on the cylinder same cylinder
good even compression on all cylinders. I only notice the oily exhaust port from the missing cylinder.
If it's wet oil, I'm starting to think leaking valve guide seal given the good compression. If it's water, maybe try filling the radiator/reservoir to the top and look for bubbles, or check for hydrocarbons with a gas analyzer. I think the engine can turn off the fuel injector to a known dead cylinder to protect the catalytic converter. It sounds like the injector is a reaction not a cause? Im no expert but those are my thoughts. I would like to know what you find.
