Mini explosive noise when starting

[NJFordDude]

Ford Explorer 2008 - 4.6L Engine - 114,000 miles

When starting the car there is a little bit of an explosion sound for lack of a better term and then it goes away. Doesn't happen all the time and happens more often when the car is being started cold. The check engine light does not go on at all and the car runs fine with no hesitation. Sparks plugs were all replaced around 90,000 miles along with one ignition coil that was failing and causing misfires.

When I looked over the engine I saw one particular part that had a lot of soot around it and the link below will take you to a picture. The area with the soot has a black circle around it. The picture may not be oriented correctly when you view it.

https://app.box.com/s/yy9n3rv452cfmp67w4bb

I am taking the car in for service and was just looking to get an idea if this might be the source of a problem and if anyone had any ideas.

Thanks in advance.

 

[Flag Gibby]

That is your knock sensor that has the most soot around it, but the hose next to it is your PCV valve and needs to be replaced with the mileage that the engine has on it. It is possible that the exhaust gases are coming from the bottom of the PCV valve and maybe from the seal on the knock sensor. The issue may be with the PCV valve not working correctly and allowing too much crankcase pressure upon start and that is the sound you are hearing.