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.

asked by on April 04, 2017

I have replaced coil packs and spark plus. Cylinder 5 misfire and low engine pressure on passenger side. Had a head gasket repair. Head was resurfaced and bent valve corrected. Still having low pressure and misfire. Engine runs little rough. Was told my mechanic that the crank and cam sensor are good. Injectors are good. What is the problem. It is driving me nuts

My car has 155000 miles.
My car has an automatic transmission.

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.

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