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Old 08-04-2008, 09:40 AM   #1
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Default My car ran without CAS

I was working on my car this weekend. There was a cable that had rubbed against the accessory belt and had split. I decided to go in and solder what I thought was a connection to my air conditioning. Once I got the under cover off I quickly realized that it wasn't connected to my AC at all but was my crank angle sensor. How is this possible that my car could start up and run decent (probably not the best but seemed fine)? It had been running like this for quite a while.

I soldered up the destroyed wires, plugged in the sensor, reset the computer and it ran without the Check Engine light which was there before.

Last edited by Big Boy; 08-04-2008 at 09:51 AM.
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Old 08-04-2008, 10:19 AM   #2
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Year?
96-97(which has a CAS on the exhaust cam also)?
99+(which has a sensor on the intake cam gear too)?
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Old 08-04-2008, 10:25 AM   #3
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Yes it is a 1997. That is interesting. What is the benefit of having 2 CASs besides the car still being able to run?
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Old 08-04-2008, 10:34 AM   #4
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On a 97 the engine probably runs off the CAS at the exhaust cam still and the crank pulley trigger is probably used for OBDII diagnostics. Aids in determining what cylinder has a misfire etc.
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Old 08-04-2008, 10:36 AM   #5
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Thanks for that bit of information. I don't know how applicable it will be after this week though. I should be getting Megasquirt installed in the next couple of nights.
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Old 08-04-2008, 10:38 AM   #6
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Are you gonna be running an MS using the cam sensor setup or the newer crank trigger?
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Old 08-04-2008, 10:47 AM   #7
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I haven't thought it through fully yet. By crank trigger you are referring to the sensor I had to fix, correct? Is this simply setup in megatune? If I eventually go with some adjustable cam gears could that throw off the cam sensor?
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Old 08-04-2008, 11:35 AM   #8
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I believe it's not simply a software setting. I only base that on DIY asking me how I wanted an MSI built recently for an MSM. I opted for the NA CAS setup since I have no experience with the crank pulley trigger.

If you ask me, doing with adjustable cam gears stands more of a chance of screwing up your electrical timing if you are determining timing based on cam position. Typically we determine timing relative to crank position. We just use the cam position to set it because with a fixed cam gear the position of the cam relative to the crank should be identical every time not taking into account timing belt stretching. If you start moving the exhaust cam relative to the crank I would think some compensation would have to be made in electrical timing. If you advance the exhaust cam gear 2 degrees you are advancing the electrical timing too, 4 degrees I think since 2 revolutions of the crank = 1 revolution of the cams.

If you set timing at crank by the actual crank position with crank pulley trigger the electrical timing is locked to the crank position no matter how much you move your adjustable cam gear.

anyone?
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Old 08-05-2008, 12:11 AM   #9
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You'll need to build the VR input circuit for the crank sensor (on the '96-'97 cars it truly is a naked VR sensor, rather than an open-collector hall sensor as in the NBs) and you will also need to build a second input circuit and wire up the CMP signal from the CAS (as per a "normal" NA install) to provide an absolute TDC reference.

If you're using an MS2, some fancy software config in MegaTune and you'll be up and running. With the MS1 CPU, you'll need to physically grind off the two teeth which are under the sensor when at TDC and BDC.


And Paul is 100% correct in that the '96-'97 cars use both CAS signals for primary operation, with the crankweel purely for OBD-II misfire detection. Starting in '99, the crankwheel became the primary firing trigger.
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Old 08-05-2008, 10:12 AM   #10
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Thanks for the helpful response.
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Old 08-05-2008, 01:51 PM   #11
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I can testify on this one - no crank angle on 99-00 = no run even with the intake sensor.... I'd have to agree with Paul in that it's reversed on the 99/00 cars (top one is for OBD2).
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