N54 Engine Air Leak

Valve cover, near the oil filler cap

Engines today have a very complex system to manage what goes inside them, as far as air and gas goes. They have various sensors that the engine computer (DME) use to regulate how much gas the injectors are going to inject into the cylinders depending on how much air is going into the cylinders. The DME is smart enough to make adjustments if the mixture is a little off, but if the mixture is off too much, then the engine is gonna run like crap. This is the valve cover of an N54 engine (the plastic cover that sits on top of the engine). We've seen a few of these engines that come in running bad, with lean mixture faults (there's too much air going into the engine, so the DME can't keep up with the amount of gas that is needed for the engine to run right). When we do a smoke test we've found a common spot on these engines that are leaking air. The valve cover cracks at this specific spot. It's easy to spot, and it's the first place to look when you have these faults.

Can you spot the crack?

It's right next to that fuel injector line. That slight crack causes havoc.