Weird VVT angle / no start issue
06-11-2018, 04:57 PM
#1
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Weird VVT angle / no start issue
So my VVT Miata won't start. Stock unopened VVT engine with 50k miles and a MS3 Pro PNP ecu.
When trying to start it I get sync errors and I have attached a composite log.
If I try to start it now it will barely start for a few seconds and sounds like it is missing pretty bad. However... If I manually put the VVT into test mode and force the VVT duty to 60-80ish percent I can get it to start and run rough. Then if I switch it back off of VVT test mode into normal VVT operation it runs perfectly and shows a VVT angle of 0 (or near zero when free revving)! This switchover has to happen in that order, even if I get it running perfectly and shut it off it won't want to restart.
VVT angle shows to be solidly stuck at 275 degrees in the last log while the car was running. My wife was driving the car on track and appears to have over reved it and after that it gets a ton of sync errors. Screenshot of that is attached.
When trying to start it I get sync errors and I have attached a composite log.
If I try to start it now it will barely start for a few seconds and sounds like it is missing pretty bad. However... If I manually put the VVT into test mode and force the VVT duty to 60-80ish percent I can get it to start and run rough. Then if I switch it back off of VVT test mode into normal VVT operation it runs perfectly and shows a VVT angle of 0 (or near zero when free revving)! This switchover has to happen in that order, even if I get it running perfectly and shut it off it won't want to restart.
VVT angle shows to be solidly stuck at 275 degrees in the last log while the car was running. My wife was driving the car on track and appears to have over reved it and after that it gets a ton of sync errors. Screenshot of that is attached.
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06-11-2018, 04:59 PM
#2
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Oh also my initial diagnosis based on the sound when trying to get it running was that it slipped a timing belt tooth. So I have already confirmed the timing marks are all good. At this point my intuition says something in the VVT actuator is bad.
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07-31-2018, 10:50 PM
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So I have the car fixed. First I ordered a 36-2 wheel from FM. With that the car would run but no VVT. I could drive it around fine with the actuator unplugged. I also replaced the cam sensor twice. From there with more diagnosis I tried resetting the min and max numbers for cam angle. It was originally 275-318 and I think I had to go to 254-298 and after that everything runs fine.
Based on what I was seeing I tend to think that the toothed wheel on the cam slipped. Another post on here mentioned that it had happened to them.
Based on what I was seeing I tend to think that the toothed wheel on the cam slipped. Another post on here mentioned that it had happened to them.
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