Another LostSync issue
 

Hello, i know this have been faced many times, but i need some support :)
MS3x on a 1991 Miata with VVT engine swapped, oem ignition retained, cam and crank sensor harness home made, cheap aftermarket crank sensor from eBay, the car runs fine and smooth until about 4000rpm, then lost syncs and misfiring. The fact is always at the same rpm's would point me on vibrations and maybe a faulty sensor, more than noises.. what do you think?
Here's composite log

Tested with an old ms2, everything works fine, what could be on the ms3x?

Trim pot adjustment?

I dont have them on ms3x, trying shielded wires today, next step Vvtuner and ms2 :D

Could you post a pic of your ms3x. AFAIK, they all have trims pots.

When you say it ran with ms2, was it with the exact same wiring or are you swapping things?

You say oem ignition retained but then say cam and crank sensor home made and mention aftermarket crank sensor. Does this mean oem ignition coils and igniter but everything else is modified or are you somehow still using the cam/crank sensor on the back of the head? Also, are you feeding 12v or 5v to the cam/crank sensors? What are your pull up resistors and to what voltage?

I used to run a DIYPNP (ms2e) with VVTuner with oem VVT sensors on pass through connections. I went to ms3 (ms3pro module) and had to make some adjustments with pull ups and whatnot. No way would I ever go back to ms2 anything.

I can't now, car recovered in the garage for the week, but i will asap.

Yes, exact the same, just disconnecting and reconnecting on the oem connector under the dash, while writing the ms2 owner says "yes but my ms2 comes with max9926" if that matters...

Yes, retained ignitor and coils from the 1.6. I did a custom made harness following this diagram, to enable NB sensors. Aftermarket i mean not Mazda genuine units but same part different brand, much cheaper.
https://cimg4.ibsrv.net/gimg/www.mia...956951cb52.png

Today i put a 10k resistor between signal and ground, same story. But enabling the VVT gave me about 1000rpm's more, i can cruise til about 5000rpms now, as for the log attached.
https://cimg1.ibsrv.net/gimg/www.mia...6c661b07de.png


Unfortunately had no time to try the shielded wires, plus i'm not sure that CAT6 are suitable for testing this application, maybe a microphone cable?

A doubt.. why i would get an error 31 (cam) when in the composite i can see there is missing teeth signal for the crank?

This Is solved... The third brand new hall sensor was the good one.