How low does compression have to be to cause a misfire or dead hole?

 

about 0.0:1. The cylinder may fire, it just wont contribute as much to the power of the engine. If you are taking compressions tests, post the results. You generally dont want to see a difference of more than 10psi cylinder to cylinder, any more than that and you have some problems. Not to say its toast, but its certainly not the best. I have seen engines that have a 30psi difference run for a long time, just not the best, or cleanest.

 

The story:

A constant misfire developed. Plug removal showed cylinder #4 had a missing center electrode (std bosch copper). No other apparent damage to the plug.

Compression test revealed cylinder #1 way under spec at 40psi. Other cylinders are ok. Leak down not completed yet.

Question is, would cyl #1 even fire?

 

40 psi is horrible. My compression is between 190 and 200 psi on all cylinders. 40 means you have either a really shot ring, your headgasket is blown at that cylinder, or one of your valves isn't sealing all the way.

 

There seems to be a pattern of this. SOmeone should sticky something on the bosch spark plugs. A customer of ours installed some bosch plugs in his truck. It ran great for a week, then started running like crap. He brought it to us and when i took the plugs out I almost died. The center of 5 of 8 plugs broke out, and fell past the ground strap into the engine. It put a hole in one of the pistons and hosed the engine. He is waiting for some kind of compensation through bosch now.

Sounds eerily familiar to me.