l have a 1999 Mercury Sable and the cam-sensor broke off, we opened up the engine and saw that the chain had come off and we think thats what cause the cam-senor to break.l wanted to know if anyone knew how the chain could come off? Also the car is only worth like $2,000 or $3,000 do you think it would be worth it to fix the car? Thanks for any response... inless its a dumb respone LOL

They wear out over time. You are suppose to change them every so often. Your car manuel should tell you. Sometimes as often as 10,000 miles

If the car is equipped with the 3.0L OHV V6 (eighth digit of VIN 'U') l would bet my life that the cam SYNCHRONIZER (the part that the cam sensor bolts to) seized up, & u happened to experience the worst possible outcome of this failure. Typically, what happens is the body of the synchronizer sludges up, restricting free movement of the shaft. Normally when this happens, the typical symptom is a loud squeeling sound is heard, extremely similar to a belt noise accompanied by a rough running engine, sometimes stalling. Normally, the repair for this is to replace the cam sensor & synchronizer which costs about $200 to $300. With the timing chain broken, u may as well replace the engine itself, since the engine needs to be removed to replace the chain anyways. To keep costs within reason, u may want to opt to replace it with a REPUTABLE salvage yard engine. This way u have some kind of warranty. Hope this helps.

l assume your talking about the timing chain. Is this an interference or non-interference engine? l just went on and they reference a timing belt, not a chain. What chain are you talking about?

The car is NOT worth the repair. 1999 mercury.
check the blue book.