E46: Inlet full of oil! Re-con time.

Removed the inlet-manifold to check the CCV [crankcase-ventilator], crankshaft-sensor and main wiring-loom / connections. It didn't look too bad underneath, though there are some signs of a stuck CCV valve. I put the manifold down next to the car while I was working and after 5 minutes I noticed a large pool of dirty oil had run out of the throttle-body, so I placed that end in a bowl, jammed the butterfly open and leant the manifold on its end. Another 1/4 pint of oil ran out of it and today I removed the throttle-body entirely and managed to get about half as much again. More is coming, so I've blasted carb-cleaner back through the inlet-ports and left it to run down.

So either the piston-rings are completely shot and are leaking that much oil back up into the inlet, in which case the engine wouldn't run... or it's one heck of a stuck CCV. In this case, it would appear the crankcase-vent valve has stuck closed, which is allowing pressure to build up and pump oil back through the clean side of the CCV-system, dumping it right into the top of the throttle-body! Rather than creating a vacuum in the air-inlet that keeps the car at a decent idle, the CCV is pumping combustion pressure instead and covering all the sensors with hot oil. Not good. This is the most poorly engine I've ever seen.

While the throttle-body is off I may as well give it a good clean, along with all the sensors that had filled up to the wiring-connector with the pressurised oil. Even if this doesn't completely clear the rough running faults, it has certainly given the engine a new lease of like and it never does any harm to flush everything out and eliminate any further problems in the inlet.