Got a 99 Durango that had a misfire code (cylinder 8). Plugs, wires, cap and rotar, injector all ok. I did a compression test, and the pressure is low (@ 50). Any ideas common problem? Head gasket? Valve?

Thanks

 

Try doing a wet test. Add oil to the cylinder and recheck the compression. If it comes up over a 100, then you may have a sealing problem. If it stay the same, then you may have a burnt valve or seat.

 

^ YEP ^


The trick he's talking about is:

If you find a low cylinder pour a couple of cap fulls of clean oil into the cylinder through the spark plug hole then redo the compression test on that cylinder. If it gets more psi then it's piston rings and you need a rebuild on the entire engine or at least the rings on that cylinder. If the numbers are the same or close then it's a head gasket, or valve.

Also you can also remove the oil plug VERY slowly and look for coolant after the truck has sat overnight. Oil floats on water so antifreeze will be the first to come out.

Also look at the antifreeze in the radiator to see if you have floating oil spots (Brown or Black).

Finally, look at the exhaust for steam out of the exhaust.