Q: I have an 4.7 HO engine for my jeep. Cylinder 5 misfire and low pressure on passenger side. Replaced spark plugs and coils.

Hi there. To be completely honest, anytime a head gasket service has been completed, I typically throw "common causes of an engine cylinder misfire" out the window. In most cases, a head gasket gasket fails due to an overheating problem. Although most mechanics will spend lots of time resurfacing cylinder heads, replacing valve guides or bent valves and push rods, what they tend to forget is that when an engine overheats, it typically destroys electrical harnesses and sensors. The first thing I would recommend is to check all ignition system electrical connections; especially to crankshaft and cam position sensors. A damaged or exposed electrical harness might short occasionally, which can cause the inconsistent misfiring problem. The low engine pressure on the passenger side might be a symptom of the cylinder five misfire issue, but could also be damage to a piston ring caused again by the head gasket failure.