Re: Progressive Misfire - P0305
Did you already swap the plug and coil from cylinder #5 with an other, to see if the fault follows?
So the problem is not fuel related. You could also try a seafoam treatment (or an other product which removes carbon buildup). A sticking valve due to carbon buildup on the valve stem could be the problem. Best is to feed the cleaning fluid through the brake booster vacuum line, without the engine stalling, and then shut the engine down and let the fluid do its work for an hour or so. Then take the jeep for a spin, but be aware that a lot of smoke will come from the exhaust. Sometimes this treatment must be done more then once to get the stems real clean.