Bad CAS??? Datalogs of voltage inside!

[jspaeth]

Some of you have been following my thread in Engine Tech where I am trying to hunt down a pain-in-the-ass misfire (across the board I believe) that occurs above a certain RPM, and the problem only kicks in after about 15 minutes of driving the car (CAS sensor getting hot and failing???)


Today I went out and logged the voltage on pins 22, 30, and 31.....two of these are 180* signal, and one is the 1* signal from the CAS....I double checked continuity between the CAS plug and these pins just to make sure I had the right ones, which I did...

*** I am not showing both 180* logs, because they agreed with each other essentially perfectly.

The FSM says the 180* signal should oscillate between 0.3-0.6 V and the 1* signal should oscillate between 2-3 V:

http://i947.photobucket.com/albums/ad316/golfertilltheend/Car%20Stuff/Diagram.jpg



Now, here are the RPM vs time for two runs....notice that the misfiring starts around 4800-5000 RPM in both cases, where there are bad oscillations in the RPM....these were done at light throttle, essentially ZERO manifold pressure, and I can confirm that the AFR the whole time were in the 13-14.5 range....not too rich at all...

http://i947.photobucket.com/albums/ad316/golfertilltheend/Car%20Stuff/RPM.jpg



1* signal:

http://i947.photobucket.com/albums/ad316/golfertilltheend/Car%20Stuff/V1.jpg


180* Signal:

http://i947.photobucket.com/albums/ad316/golfertilltheend/Car%20Stuff/V180.jpg




The 1* signal seems to usually be around 1.3-1.5 V, which is lower than spec a little....but there are some spike that take it well outside of the 2-3 V range.


The 180* signal seems AWFUL....it spends a lot of time down there between 0.3-0.6 V, but there a shit ton of spike that take it WAY WAY WAY outside of that range.


People with experience:

Are these types of fluctuations normal?.....or does it certainly look like this is a case of a bad CAS???

[greenman100]

What'd you sample with?

At 6000rpm, you're looking at pulses of 360*100= 36000hz. Then, you should have at least double that frequency for your sampling frequency - 72khz.

Are you datasampling that fast?

Honestly, just swap the damn CAS. takes 10 minutes. If the money's a big deal, you can always resell it for at least 80%.

[yabeet]

Dont you have any friends with SR's locally? Just borrow their cas for an hour, Im sure if you reinstall their cas afterwards and time it with a light they would be happy to help you out.
You are a pretty freakin smart guy, but I think you are making a mountain out of a molehill here when you could just swap with one that you know works good off someones car?

[jspaeth]

What'd you sample with?

At 6000rpm, you're looking at pulses of 360*100= 36000hz. Then, you should have at least double that frequency for your sampling frequency - 72khz.

Are you datasampling that fast?

Honestly, just swap the damn CAS. takes 10 minutes. If the money's a big deal, you can always resell it for at least 80%.

I am not really prepared to just fucking spend $350 on a brand new one when I am not 100% sure that is the issue in the first place.....

ANd yes, your point on sampling is correct....the FC datalogit probably doesn't sample fast enough to see smooth data....

Perhaps the spikes are when the sensor is seeing and "opening" in the disk....so for the 180* signal, it doesn't see the openings very often...

Maybe the data that I logged is okay? I am beyond frustrated with this problem.

Dont you have any friends with SR's locally? Just borrow their cas for an hour, Im sure if you reinstall their cas afterwards and time it with a light they would be happy to help you out.
You are a pretty freakin smart guy, but I think you are making a mountain out of a molehill here when you could just swap with one that you know works good off someones car?

That's the problem, there is no one that I know that lives within 2 hours of my house of an SR...

Obviously, there probably are plenty of people, but I just don't spend a whole lot of time hanging out in the tuner scene, so I don't really know anyone.....

This is so weak.

Now the problem has gotten worse, and the misfiring at 4-5K RPM probably is occuring right when the car is first started....