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-   -   NB2 VVT Sync Loss/No Start (https://www.miataturbo.net/megasquirt-18/nb2-vvt-sync-loss-no-start-108023/)

crispyBYM 03-16-2023 03:28 PM

NB2 VVT Sync Loss/No Start
 
8 Attachment(s)
Hey everyone, I've got a solid issue with my new to me MS3pro that hopefully someone can help guide me in the right direction on understanding and fixing.

Description:
This issue is brand new. I got the car running on MS3pro on 3/12 and set base timing and messed around with fueling/idle to get AFR's and the car in a nice driving condition. Did some street tuning with VE Analyze however did not change much as the car would start up and idle and drive smooth. Two days later I go to drive the car and am greeted with the following issue. Car does not want to start/will start but not idle well. Taking a normal log of the issue shows sync loss/RPM drop to zero with a Sync Error of 31 and 32. In the car you can hear relay clicks each time this sync loss occurs and RPM drops to zero momentarily before bouncing back. I was able to get the car to run on one occasion post-issue and the car idled like normal before a sync loss caused the car to die instantly. Below is a YouTube video of the condition.


Car:
Unopened 165k mile VVT motor
Used MS3pro
Brand New OEM Crank Sensor installed ~5k miles ago due to physical damage to the sensor
Original Cam Position Sensor
No recent work to timing belt or anything that would change mechanical timing from when car was running on both Stock ECU and MS3Pro (mechanical timing not verified)

Musings from an Idiot:
My best guess is that the cam position sensor may be causing this issue as they are such a common issue on these cars. I have a $20 Amazon sensor coming to see if that makes any changes. The car running fine to not running at all seems to indicate a failure of some sort rather than an issue with the tune. To "verify" this I reloaded the base map for the car to see if the issue persists, it did. Additionally I don't think that mechanical timing as when I shut the car off from it's last drive there were no issues whatsoever. Additionally the one time I have been able to get it to idle since then the car was normal before a sync loss killed it. The one hesitation I have is with the bouncing tach/relay clicks the occur that might indicate some electrical issue that hopefully someone might recognize.

I've attached both a regular and Composite Log as well as the tune to see if there are any glaring issues. Any help would be much appreciated. I've scrolled through a lot of the issues that other people have and have tried some of the quick fixes (zipties on CPS connector, etc) but with no improvements. I've scrolled through the Composite Logs and I honestly don't see anything abnormal when it comes to where the log shows sync loss vs. when it shows normal operation. Additional to the help any education on this matter so I can understand what it causing the issue would be great as well. Any learning moment is a good thing. Thanks!


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