2000 Civic EX, 84K miles, 5 speed manual.
While slowly accelerating from a full stop, my car seemed to hesitate for a couple of seconds. It then paused and I heard and felt a sharp " knock" in the engine, I also noticed a vibration hitting the hood from the inside each time one of the pistons fired. The engine didn't shut down as if the timing belt had failed, though. I was able to slowly pull out of traffic and, after rasing the hood, found that one of the sparkplugs on the row closest to the front of the car, was raised up completely out of the head; sparkplug wire intact. The sparkplug threads did not shwo any signs of having been stripped before coming out of the head, but around the plug just below the ceramic is a hard, black plastic sleeve. When I slowly pulled out of the traffic, I felt and heard a hard knock each time that piston came up to meet the plug. I didn't have to travel more than a few feet to get out of traffic, and thena t that time I turned off the engine and have not retarted it.
Any assistance is greatly appreciated.
Dont hear this happening everyday. When can talk about why it happened, but first off you will probably need to take your car to a machine shop and see if they can repair the threads of the head. A heli coil may can be added to allow you to screw in a new plug in that hole, and not have to remove the head.
As to why, well some of the Honda engines have very tight clearance on their heads. If you arent careful, you can place a spark plug in it that is too long. If this was the case, then there may have been some damage to the piston also. A compression check and time will tell you the story about that.
If it was not a too long plug, then maybe the plug itself was defective causing it to come apart, and the threads are still in the head. Here again a machine shop might be your best bet. I would see if the spark plug threads are still installed, and maybe you can back them out carefully. But dont mess around and screw up the head. $$$$
Another thing can just be a defect in the casing of the head. If it is a small one centralized at the threads, then maybe a machine shop can tap it out and insert a heli coil for you.
Have I mentioned machine shop?