2JZ vvti, cam sync disappears on low rpms (probably solved)

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Gonis
Posts: 4
Joined: Mon Jun 18, 2018 8:38 am

2JZ vvti, cam sync disappears on low rpms (probably solved)

Post by Gonis » Wed Jan 16, 2019 10:14 am

Hello everyone, I have strange issue with cam sync. As far as I search I found only cam sync issues on high rpms, that is from electrical noise. But on my case, the issue appears only on low rpms, or when cranking.
Symptoms:
1) At first I randomly couldnt start the engine, it just backfired from intake manifold. After few minutes it starts instantly. Some time later I set cranking parameters, that on cranking event injectors would be batched and spark ignition would work on wasted spark. Now it starts every time, just with different results. Almost every morning it starts, but then it is working on 2 cylinders at best (no cam sync). The sync appears only when I rev up engine high enough (sometimes to 2krpms, sometimes it need to be reved up to 4krpms). From then engine runs fine, because option "enable sync w/o camsync" i enabled. If the engine is warm, then it starts normal at ~80percent of the tries.
2) vvti cam angle gets 'stuck'. At first I thought its a bad vvti valve. So I changed to another used one (with no results) and even to new one (again, no results). Then I realised, that this issue could be result from randomly missing cam sync. Ant after some logging it is clear, that this is the case - when "cam sync present" turns to "NO", vvti angle gets stuck on last position. The only option to gain cam sync again is to rev up the engine high enough.
If I disable vvti valve then engine runs fine (just the starting issue is left)

Things I done - changed CAM sensor and its wirring (high quality shielded cable. Shield is connected to chassis only on one side). Maybe the parameters are not set properly or I need to set additional pullup on signal wires? Im sceptical about this option, because first few months there was no this issue. It only appeared after some time. I attach my curent parameters and print screen from log when vvti gets stuck.

Thanks in advance
Attachments
vvti stuck.jpg
vvti setting.JPG
trigger crank settings.JPG

Gonis
Posts: 4
Joined: Mon Jun 18, 2018 8:38 am

Re: 2JZ vvti, cam sync disappears on low rpms (probably solved)

Post by Gonis » Wed Feb 06, 2019 9:31 am

After changing the polarity of CAM sensor these issues dissapeared (so far). Also after that the trigger edge needed to be changed to 'rising' (engine does not run with CAM sensor falling trigger edge anymore). Dont know if its the right way to solve this problem, but the engine runs good so far (just need to fine tune the timing)

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