Crank angle sensor "kind of" working?

[kumpe]

Hi everybody, I would like to start off by thanking everyone for a great forum, I've been reading a lot since I got my Pajero Sport a few months ago, but this is my first post.
Keep in mind that I'm swedish, so please have patience with me if I'm using the wrong technical terms or if I'm hard to understand in general.

My Sport began acting up a while ago. First the check engine light came on once in a while but it kept going like nothing was wrong. Fault codes indicated a problem with the crank angle sensor.
A few weeks ago it started vibrating and lost power all of a sudden while driving, and the rev counter started showing around half as much as it should. It runs really poorly, kind of like it's not firing on all cylinders.
Measured the output from the CAS while cranking the engine by hand, and it seemed fine.
So to rule out timing belt jump or a misaligned reluctor plate I started tearing into the engine, and now I have confirmed that none of these are the problem.
I also measured the output from the CAS while watching the position of the reluctor plate, and the output seems ok in both timing and voltage (0,1V while off, 4.9-5V while on), but I suspect that it actually is broken anyway and the signal isn't "good enough" for the ECU somehow.

Has anyone seen this before, a CAS that still works good enough to keep the car going but still needs replacement?
Anyone have any other theories on what could be wrong?

[msman]

on other makes have seen crank sensors which are ok most of the time but have degraded internally/casing and loose signal with heat or moisture.
so you test them while diagnosing and the sensor tests ok but start driving thru rain or after a thorough warm up and the problem starts.

the other thing to check is the wiring, bad connection in the loom or a rubbing cable.

best of luck.

[Rainmann]

ECU Reset

First off I would check the CAS connections to make sure there is a good solid connection, if you think there was a loose connection then try a ECU reset, if you don't think there was a loose connection or some other possibility of a short or spark that could cause a power serge, then replacement of the CAS couldn't hurt.
ECU reset- Sometimes electrical issues can cause the ECU to receive corupt signals and it tries to compensate when it makes these adjustments to the stock settings it stores them in memory, however sometimes this memory gets corupt or loads conflicting map adjustments and confuses the ECU, depending on the year of your vehicle this memory has stored hundreds of adjustments and been rewritten so many times. Resetting the ECU erases the memory and the ECU creates new maps starting from the stock firmware removing the possibility of incorrect settings being loaded.
Remove the negative lead of the battery and only the negative lead for 1min, then reconnect start the vehicle and let idol for 15 min during this time the idol might fluctuate this is normal it's the ECU taking control and relearning. See if this helps ( depending on age and/or level of memory defrag this procedure might need to be preformed more than once.)

[kumpe]

Well it turns out it was the CAS after all. Got a new one today and got it in this evening. Now it runs just fine, at least while standing still, I had a beer or two while putting it back together so I didn't want to drive it at the moment.

So, what have I learned from this? Well, that the CAS apparently can make your engine run like s**t without being totally broken, and even though you can measure the signal from it and it seems normal the ECU doesn't necessarily agree with your findings, and that the tacho behaving weird is might be a good indicator that something is wrong with this sensor.

Thanks for your help and input!

[kumpe]

Aaand I spoke too soon.

Started up my car today and went for a drive around the block. The car is running as smooth as ever. I park in front of my house to unload some tools and let the car running on idle. After about 10-15 minutes the engine suddenly starts to misbehave again in the exact same way as before, and the CEL comes on.
Now I'm starting to run out of ideas, what could be the cause of this? Bad ECU? Some sensor feeding the ECU with bad signals once it gets warm?
I will check and recheck all the wiring from the CAS but I seriously doubt that is the problem.
Anyone?