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MS2 crank signal noise


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I am having rpm loss and crank signal errors while cranking, and while running below roughly 1400 rpm. The car will start with some throttling and run great around or above 1400 rpms. Once I let off the throttle, the car will buck and die. While composite and teeth logging during cranking, I'm not seeing anything close to a proper tooth count, and the rising/falling edges look blocky. I'll attach both composite and teeth logs below as Excel and Megalog files as well as my TunerStudios file.

I've confirmed the jumpers J1 and JP1 are correct for the Nissan CAS optical sensor. There is a 1k pullup resistor wired from the injector 12v to the white(pin24 i believe) crank sensor signal. I've readjusted the R52 and R56 pots according to the manual. I read 2.39v at the top of R54 and can't seem to get it any higher while turning R56 clockwise. I have had the car running well previously and I decided to upgrade the fuel system and reroute some wiring to clean it up a bit and am now having these issues.

My hardware and settings are as follows:

MS2 V3.57 board with a BIP373 transistor
3.4.2 firmware
Nissan CAS optical sensor with the DIY 12-1 toothed wheel
Single nissan ignition coil
-Falling Edge
-Going high
-Single coil
-JS10 (jumped to igbtin within board)
Wiring is per MS2 v3.57 schematics. CAS power is fed from an unused relay terminal.
No Idle valve
1050x hi z injectors
walbro 255lph fuel pump

BCPR6E-11 resistor spark plugs and NGK wires


I've confirmed the MS has 12v+ and both power and ground leads are good with <0.2 ohms respectively. I've tried moving the MS grounds around the engine bay, from the heads to the intake manifold to the firewall. I get the same measured resistance across each ground position. There was no change in the messy signal.

I then tried isolating the noise by:
disconnecting the coil. No change.
separated the shielded wire from the injector wires. No change
(Note: the only un-shielded portion of wire for the crank sensor is where I connected the wires to the stock CAS and for the pull up resistor from the +12v injector wire).

Unable to find any noise reduction from obvious *loud* wires, I then readjusted the hysteresis and trigger voltage pots R52 and R56. No change

Then within tunerstudios, I introduced 25% noise filtering at .1ms and I can see what seems to be some semblance of square waves. The tooth log still looks as ugly as it did with or without filtering. I'm considering changing out the CAS with a fresh one as I have no way of testing whether its malfunctioning or not. I would prefer not having any noise filtration if that's even possible. I don't like the idea of putting a bandaid over bad wiring.


Thank you!

Z31 1.msq cranking tooth logger.mlg cranking tooth logger.csv cranking composite logger.csv cranking composite logger.mlg

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Well good news. I got to thinking about how I lost my trigger signal beings I had only changed 2 things, injector impedance and wire routing. So I got to digging about hi vs low impedance and the effects of noise. Well I began to realize that I had my CAS signal (pin 24) pulled down with a 1k ohm resistor from the 12v+ of the HIGH IMPEDANCE INJECTORS. I had removed the PWM ?filtering? for the low impedance to high impedance injectors. So I moved the resistor to the CAS 12v+ and voila, perfect trigger edge, and some slight deviation of around 2ms of the teeth in the tooth log 


The impedance or pwm control must have been a big factor as to why it worked previously that way. Anyway, thought I'd update this post with a success!

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