Misfire solved

[Bryanbones]

Bought my first tj and had a miss in it.Its a 2000 sport with a 4.0 it would pull code p0305 number 5 cylinder miss.this drove me crazy for two weeks trying to figure it out.things I done new plugs coil pack o2 sensors new crank sensor cam sensor tps map sensor 150 psi on all 6cylinders no vacuum leaks went all though the wires changed injectors 5 with 1 didn’t help the miss was still there I could pull injector plug off and it would change the sound of the engine but not as much as the others so I thought it has to be something in the head but with 150 psi on the cylinder you wouldn’t think so.so I pulled valve pan off and checked the rockers and everything looks good.so I started to crank the engine over and there it was all the push rods was turning except for numbers 5 cylinder the valve on that cylinder had stretch somehow cause it not to close all the way letting it miss fire so long story short got a few shims under the rocker cleared codes and no more miss fire so I hope this helps some body and don’t give up when you get a miss fire I didn’t now I’ve got a good looking and running tj

 

[TJProjectRon]

Bought my first tj and had a miss in it.Its a 2000 sport with a 4.0 it would pull code p0305 number 5 cylinder miss.this drove me crazy for two weeks trying to figure it out.things I done new plugs coil pack o2 sensors new crank sensor cam sensor tps map sensor 150 psi on all 6cylinders no vacuum leaks went all though the wires changed injectors 5 with 1 didn’t help the miss was still there I could pull injector plug off and it would change the sound of the engine but not as much as the others so I thought it has to be something in the head but with 150 psi on the cylinder you wouldn’t think so.so I pulled valve pan off and checked the rockers and everything looks good.so I started to crank the engine over and there it was all the push rods was turning except for numbers 5 cylinder the valve on that cylinder had stretch somehow cause it not to close all the way letting it miss fire so long story short got a few shims under the rocker cleared codes and no more miss fire so I hope this helps some body and don’t give up when you get a miss fire I didn’t now I’ve got a good looking and running tj

Wondering how you had 150 lbs on test with valve not closing. i may have misunderstood what you were saying.

 

[BlueFl.Wrangler]

What did you use for shims? How thick? What was the total you ended up raising in thousandths?
Thanks

 

[CodaMan]

I'm confused. For a valve not seating enough to cause a misfire how could it have 150 psi of compression? The unseated valve would not allow the fuel to be compressed enough to be ignited by the spark plug.

 

[Bryanbones]

I don’t really know but it had 150 on it.the only thing I can think is it would seal while checking it but when it was running it would be just opened enough for it to miss fire.