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28 Losses of Sync in 30 secs

Old 04-27-2019, 06:05 AM
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Default 28 Losses of Sync in 30 secs


I was on my way to Summit Point when the car had a little stutter. TunerStudio was running and indicated three losses of sync. I started a log and drove for a while without issue. During this log I had 31 losses and 28 within about 30 seconds. The car felt like it was going to die completely. I saw the battery light start to illuminate. I made my way over to the shoulder, and then she started running normally again. The weather was complete ****, and I wasn't in the safest spot to stop, so I decided to keep going, if the car would, till I could pull off into a parking lot somewhere. I ended up just going the rest of the way.

I was doing some autotuning at the time. The lights and wipers were on, and the fan running at 2.

I stopped and got gas near my hotel. She started right up afterwards. After unloading the car in front of the hotel a few minutes later, she would not start. It felt like no spark. I pulled and reseated the cam sensor connector, and generally touched all the connectors and plug wires. She started normally. After parking her I replaced the cam position sensor.

Any words about what you see in the log would be greatly appreciated.
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Old 04-27-2019, 09:11 AM
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The usual mode of failure for the crank/cam sensors is that these symptoms get progressively worse as the car warms up, to the point where the car stalls and won't restart until you let it cool off for 20-30 minutes, repeat.
Originally Posted by ninerwfo View Post
The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
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Old 04-29-2019, 06:43 AM
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I always carry spares. For the cam sensor, I have made two purchases locally of the same item. They have limited lifetime warranties. I put the new spare in, exchange the bad one when I get home, and put its replacement back in the spares box.

My concern was I'd never had anything like that happen before. One stutter always equated to one loss of sync, not three like this time. And I've had a couple in a row on track on a hot day, but they were always separated by a second or two. Never 30+ in a short period of time, especially on a cool day. The log indicates the CLT was about 180 and MAT 69, so she wasn't heat soaked. I thought it might be related to the rain.

Regardless, I had no issues on track or the ride home after installing the new cam sensor.
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