First Day Tuning Issue (Lost Sync Reason 2)

[CMac89]

I was driving around yesterday and sorted out many little issues, but there is one that I'm confused about. Whenever I get to around 4500 RPM, the engine backfires. It seems to consistently do it around the same RPM. Looking at datalogs, the RPM signal drops out and there's a lost sync reason 2 (missing tooth at wrong time). I don't seem to get that until I get to upper RPMs (might even be the same RPM, but I missed logging the other times). A question I had was is this part of a spark cut strategy? Force a missing tooth error? Or is it always a legitimate error?

I checked the composite logger (attached screen shots because i forgot to save as a log first) and noticed that the crank and cam caps were pretty close, so I change the crank tooth reference to check at tooth 15 to make sure it sees high/low.

Also, I'm using the DIY Cherry Hall sensor with a 5v ref signal (1k resistor). Could this be too low of voltage and cause this problem? Thought about going 12v with a 2.4k resistor.

Please see the logs and tune.

[Matt Cramer]

Can you post a tooth log CSV of the loss of sync?

I often recommend powering the Hall sensor with 12V even if you are using a 5V pull up.

[CMac89]

Can you post a tooth log CSV of the loss of sync?

I often recommend powering the Hall sensor with 12V even if you are using a 5V pull up.

The 5V pullup with a 12v ref wouldn't work for me. It had intermittent crank signal until i went back to 5v. Constant 12v while cranking and no grounding in signal wire. I have a log of what it does with the 1k pullup that i can post, too.

Unfortunately that screen shot is the latest of what I currently have. I can post an older version of a log, which should be about the same, when I get home.

[Matt Cramer]

The composite logger is not the right tool for the job here - for chasing Lost Sync Reason 2, you want a tooth log instead.

[CMac89]

Would it be best to replicate the situation to catch it in action? Are there specific symptoms that can predict reason 2 through the tooth logger?

[billr]

"The 5V pullup with a 12v ref wouldn't work for me. It had intermittent crank signal until i went back to 5v. Constant 12v while cranking and no grounding in signal wire."

I'm a bit confused by that. Are you saying it won't work with a 1K resistor pulling the signal up to 12V; that the signal then stays steady at 12V? What supply voltage to the Hall sensor when doing that, 5V or 12V? Are you certain that sensor doesn't have an internal pull-up resistor?

[CMac89]

"The 5V pullup with a 12v ref wouldn't work for me. It had intermittent crank signal until i went back to 5v. Constant 12v while cranking and no grounding in signal wire."

I'm a bit confused by that. Are you saying it won't work with a 1K resistor pulling the signal up to 12V; that the signal then stays steady at 12V? What supply voltage to the Hall sensor when doing that, 5V or 12V? Are you certain that sensor doesn't have an internal pull-up resistor?

I was intending to state that 12v ref with a 1k pullup would not work (intermittent signal), but the same pullup will when I switch over to a 5v ref. The data sheet for the sensor states that an external pullup is needed and also gives a chart of resistances to use for a specific voltage, i.e. 2.4k for a 12v ref and 1k for 5v.

Seems like Matt has had cases where 12v ref with a 1k pullup has worked successfully. Not sure why it is not working for me.