Join Date: Aug 2011
Feedback Score: 0 reviews
Few things that could be wrong, so I suggest you perform a leak down test before you tear it apart.
1. Damaged/broken top and/or 2nd compression ring(s). In that case your cylinder wall may have been scored as a result.
2. Burnt or bent exhaust or intake valve(s)
3. Blown/burnt head gasket around cylinder #4.
4. Spun rod bearing, however, it would be accompanied by a knock, hence this is not the case hear based on your description.
5. Cracked cylinder, although I doubt detonation would cause such a damage unless you have a forced induction engine. Still a possibility.
6. Burnt/damaged valve seat(s)
7. Cracked/damaged/burnt piston top
8. There is a chance that the top and 2nd compression ring gaps have lined-up
9. Cracked cylinder head
10. The timing is off, although your compression would likely be off in all 4 cylinders.
11. Spark plug hole threads are damaged allowing partial compression out
12. Theoretically if the lobes on intake and/or exhaust cams are damaged in a certain way, it could keep the valves to stay open longer. The chance of that being the case is extremely minimal.
13. Key way(s) damaged on either the harmonic balancer, the crank, the cam(s) or the cam gears. Although the compression loss would likely be noted in each cylinder.
14. Head bolts #9 and #10 may have lost partial torque due to the weakened threads and may have backed out.
15. No, the valve stem seals would have nothing to do with it.
Last edited by Built_not_bought; 05-15-2019 at 10:50 AM.