Hi, I have a 2000 996 and it won't fire and or idle. found a lot of oil deposits in the verticle spark plug. My guess is the rings or seals are gone. 2 questions: How big of a major problem is this? can it be fixed at home?. Thanks all in advance. Ronnie

Internal engine problems could just be valve seals leaking oil into the combustion chamber pull out the spark plugs and look at them if they are covered in oil and the firing pin and electrode are bridging together then it's your rings or head gasket and the truck is smoking a lot ///if you just see plugs that look tan/white ash build up its the seals and it smokes a little after idling and then you accelerate and it disappears and then starts again after idling you will see light blue colored smoke but not clouds of it just a slight haze in the exhaust

Hi Josh:
I'd put fresh plugs in it and drive it for a week, then check the plugs.
Sometimes you will get high compression readings that are not valid because the rings are soaked in oil so they think they are sealed when they are not.
With the engine off, you could try removing the oil filler cap when the engine is hot, then restart it. A little vapour is OK, a lot indicates bad valve guides, head gasket,or ring blowby.
Also, try checking inside the exhaust tailpipe. If it is oily sooty it is also an indication of possible ring problems.
Review the maintenance history. How many miles on the engine? Could be the engine is getting tired.

The engine is burning oil if oil deposits are on the firing end of the spark plug. Possible worn valve seals/guides or worn oil control/piston rings

Could be fuel or oil fouling. Need to determine which first off. If it is black sooty fouling it is likely too rich also it too rich may be wet.

If oil fouling it is more likely to be much more material fouling and wet sticky material.

A wet, black and shiny deposit on plug base, electrodes and ceramic insulator tip indicates an oil fouled plug. The condition may be caused by one or more of the following: worn pistons, worn piston rings, worn valves, worn valve guides, worn valve seals, a weak battery or a faulty ignition system.

A dry, fluffy or sooty black deposit indicates an air/fuel mixture that is too rich, engine idling for excessive periods of time and/or enrichener usage for excessive periods of time.

A light brown, glassy deposit indicates an overheated plug. This condition may be accompanied by cracks in the insulator or by erosion of the electrodes and is caused by an air-fuel mixture that is too lean, a hot-running engine, valves not seating or improper ignition timing. The glassy deposit on the spark plug is a conductor when hot and may cause high-speed misfiring. A plug with eroded electrodes, heavy deposits or a cracked insulator must be replaced.

A plug with a white, yellow, tan or rusty brown powdery deposit indicates balanced combustion. Clean off spark plug deposits at regular intervals.

Stop the oil leak. There are gaskets and seals for wherever it's leaking. Valve cover gaskets or seals on the cover if the plugs are recessed. Is the black stuff oil that gets splattered up there?
Spark plugs can keep firing even with oil around the base, but the cleaner the better. A clean engine runs a whole lot better and cooler than one caked in oil. Just don't try to pressure wash it or you'll have worse problems.
It would help you if you could isolate a non firing cylinder, find the one that's missing, I mean. There is a way to find a miss on a running engine by isolating a cylinder that doesn't drop idle speed when the plug wire to that cylinder is removed. But please have someone do it that has done it before. They will know what spark shock means, and how to avoid or mitigate it, or anticipate it-lol. Thatsa lotta voltage!
If you pull the spark plugs out, may help you find the bad cylinder: one will look quite different, may be all black and soot covered on the bottom that is inside the cylinder. Good firing spark plugs will have a tan or brown appearance down at the bottom, with very little deposits on them. (and if black and oily looking and wet, you have likely worn piston rings letting oil burn in there.) So if you could find the miss, it will help you a lot. Maybe you need a tune-up, after looking at your plugs-are they worn down real bad?
Lots of causes for a miss: ignition (plugs, wires, rotor, distributor cap, coil even), gas related (if multiport injection, possibly an injector problem) , and also an internal mechanical problem affecting that cylinder (like a bad sealing valve, a head gasket leak: do a compression test to check for that).
I hope I have helped you in some small way. Good luck.

Wouldn't be the timing belt. Could be the idle controls, or the MAF sensor, or a dirty air or fuel filter.
Be sure and check for trouble codes. Pull the spark plugs and check their look and the plug gap. A cylinder that is firing good (good compression, good air/fuel mixture, good ignition) will have a tan or gray look with very little deposits. A lot of black, sooty deposits indicates running rich, a blistered, white pug indicates running lean. And black, wet deposits indicates oil fouling from worn rings, most likely. Check your plugs, probably good, but see if they need replacing.

Where to begin.
Any chance you can take the truck back for a refund ??
If not, you have some major expenses ahead.
If the oil is in the cylinders, the odds are you have rings and valve guide wear which would require rebuilding the engine. Replacing the valve cover gaskets would only be a concern if the oil is on the outside of the spark plugs. Fixing one thing such as rings or valves with that many miles on the truck would not be realistic.
The bearings and oil pump and so on would have 192k on them.
The timing belt and water pump should be replaced every 75,000 miles, so you should be on the third one now and another due at 210k.
The big issue is the mileage on the truck. Replacing or rebuilding the engine now would be a big investment on a truck that is close to the end of life regarding the rest of the components such as suspension and transmission. The 3.0 engine and drive train have a life expectancy of 200k in most situations. Not to say it can't last any longer, but the odds go down after that number.

You probably have a broken ring on the piston or a bad valve stem seal on that cylinder, I would guess a broken ring more times than not. RayC

If three of the four spark plugs are firing good you can eliminate the coils. Most likely if only one plug is fouling with oil it is a leaking valve seal or a broken ring. To determine which is the problem, remove all four spark plugs and complete a compression test of each cylinder. Write down the results to compare with the next step. Each cylinder should be within ten percent of the others, Now, squirt about a tablespoon amount of oil in each cylinder. If there was low compression on the #2 cylinder and the compression increases substantially with the oil inserted you have a broken ring. If there is low to no compression on the #2 cylinder you have a burnt valve. If the compression does not increase and the spark plug fouls with oil you have a bad valve stem seal.

your valve seals are worn or guides on the head. wha you need to do is take a compression test of each cilynder and when you are doing that check each spark plug for signs of oil wich means that is the cylinder with the problem so its either going to be the head or the piston rings