Timing jumped?

JoseFfs

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Hey all, I have a 2007 Pontiac g5 with the 2.2L ecotec engine, has probably shy of 200k miles on it, and up till monday it was running dandy. I took to work about 20miles there and 20 miles back. On my way back from work I stopped at Walmart to get a couple of things. Got back in the car and attempted to start it and nothing. It was cranking but wouldn't start. Thought maybe my battery was low. Had a buddy take me have it tested at the auto parts store and tested good. The starter was spinning. There was fuel pressure at the rails. I assumed the timing jumped and removed the valve cover. Timing chain was still in place, and rather tight. Now the car has me scratching my head. We read the codes on the car and we came up with a camshaft position sensor. We replaced it and reinstalled the valve cover. In the attempt to start the car we turned the key over and we heard a slight crunch. We removed the spark plugs. (We forgot to remove and check them up to this point) cylinder 1,2,3 were normal worn out. Then cylinder 4... the ground electrode was crushed pretty good. Just looking down the spark plug tube, we can see where the piston made contact with the spark plug. Now it really has me scratching my head. I would assume if timing messed up, I would have seen some kind of damage in each cylinder. So far only cylinder 4 shows any obvious signs of damage. Which has me puzzled.
Im not familiar with these types of engines so has anyone run into a similar situation? I appreciate anyone who takes the time to answer
 

munron

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When the timing chain fails or skips, the pistons collide with the valves. I believe they usually impact valves before they come high enough to hit the spark plug. Because of the way it happened I'm not inclined to blame the timing chain. Sounds more like a connecting rod which has broken. Would be very unusual but I can't think of anything else. Perhaps others can.
 

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