Cam Shaft Sensor

[hgray14]

1) Does the cam shaft sensor fail regularly on our cars (850s)?

2) If so, at about what mileage?

3) Are they an "on/off" type sensor or do they wear out over time and cause the motor to run inefficiently (like the 02 sensor)?

4) If mine hasn't failed, do I bother messing with it or do I wait until it fails?

5) Can I grab one from a junkyard or do I need to get it new?

I am asking because I was at a junkyard yesterday and noticed one was missing. Actually, I didn't even know what it was since I have only seen engines with it in place. With it gone, the engine caught my eye so I looked it up and figured out it must be the cam sensor (it is in a similar position as the distributor cap only on the cabin side of the driver's side of the engine, right?).

thanks

Houston

[Ozark Lee]

As far as the failure rate I would rate it as a low failure rate item. My '94 has the original after 237k miles. When they do fail it is very binary. It works perfectly right up to the point where it fails and the car won't run. If you can grab one out of a salvage yard for cheap it might be a good investment but it isn't the kind of thing that you do a PM replacement on IMHO.

...Lee

[hgray14]

As far as the failure rate I would rate it as a low failure rate item. My '94 has the original after 237k miles. When they do fail it is very binary. It works perfectly right up to the point where it fails and the car won't run. If you can grab one out of a salvage yard for cheap it might be a good investment but it isn't the kind of thing that you do a PM replacement on IMHO.

...Lee

I had a feeling it wasn't a PM item but seeing it gone from the junkyard made me wonder.

thanks

[troyhyde]

Grab one and have a spare. Typical failure is work / no work. Not always however.

I was having a hell of a time figuring out an intermittent miss, noticeable at idle. Put a scope on the coil wire and noted that an occasional spurious misfire would occur on random cylinders. Swapped out the cam sensor for another and the problem disappeared. Not typical perhaps but sensors tend to do strange things in their old age.

[hgray14]

Grab one and have a spare. Typical failure is work / no work. Not always however.

I was having a hell of a time figuring out an intermittent miss, noticeable at idle. Put a scope on the coil wire and noted that an occasional spurious misfire would occur on random cylinders. Swapped out the cam sensor for another and the problem disappeared. Not typical perhaps but sensors tend to do strange things in their old age.

Will do. It seems like my collection of "just in case parts" has gotten quite big but I am not complaining. Thankfully, I rarely have problems with my cars and since the parts are dirt cheap at the junkyard it isn't like I am wasting a lot of money having all these back-ups. With three in the current stable it sure is nice to not have to scramble when something goes wrong.