Hi y'all,

My 2006 Mustang 4.0 recently stated idling rough and I got a check engine light. After pulling the code, I got Cylinder 4 misfire. So I immediately did a full tuneup; i replaced all plugs, wires, and coil pack, but no luck.

I then decided to pull the Intake manifold gasket, and I noticed that there are traces of coolant in once of the intake holes corresponding to cylinder 4. I immediately thought head gasket and decided to do a compression test. The results of the compression test was extremely satisfying with no problems.

I can't figure-out how the coolant is getting into cylinder 4 intake!!!??? The car is not overheating (Yet), there is no coolant in the oil ( I do see a small trace of mixture where the intake manifold hose connects to the valve cover).

Any ideias?

Thank you all.

 

I would still change the head gasket. Maybe you caught it early

 

Disregard what i said about changing the head gasket.

Maybe the plastic intake manifold is cracked? Just something to check.