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Ignition Timing Not Advancing

Does anyone know what controls ignition timing, from beginning to end? I'm guessing that it starts with the TPS, which signals the DME or KLR. I have also read that the knock sensor will effect timing advance. My mechanic says the ignition timing is not advancing. It seems to me that it should be a fairly small flow chart to determine what could be the problem(s), so a concise test plan can be developed. I doubt it's simple, but any ideas would be appreciated.

Thanks
Old 03-06-2018, 12:55 PM
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Look at the "DME Test Plan" for direction on this.

I would also get a new mechanic...
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Old 03-06-2018, 04:20 PM
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Originally Posted by BMD273 View Post
Does anyone know what controls ignition timing, from beginning to end? I'm guessing that it starts with the TPS, which signals the DME or KLR. I have also read that the knock sensor will effect timing advance. My mechanic says the ignition timing is not advancing. It seems to me that it should be a fairly small flow chart to determine what could be the problem(s), so a concise test plan can be developed. I doubt it's simple, but any ideas would be appreciated.

Thanks
Main selector of ignition is AFM X RPM which determines which data-cell on 3D map is selected. RPM is determined by flywheel speed & reference sensors. TPS WOT switches to full-throttle 2D map. Think of that as the highest-load row on 3D map's "wall". Below WOT, TPS doesn't affect ignition at all. Here's fuel & ignition maps off a 951 (R.O.W map I think). Actual fuel & ignition values used is selected off X-Y coordinates off LOAD(AFM) X RPM scales.



Mechanic is probably old-style and thinks rotating distributor affects ignition timing (it doesn't). Find another more modern mechanic that knows how to use oscilloscope and computers for diagnostics.

Last edited by DannoXYZ; 04-18-2018 at 11:26 PM..
Old 03-10-2018, 03:09 PM
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Knock sensor input will retard timing about 3 Deg instantly. The ECU will then advance it again slowly. Give it (knock sensor) a tap with a socket extension adapter or something similar. NOT HARD !
If you have access to an oscilloscope hook it up to the output from the KLR to the DME pin 32 iirc
and you should see it. Or else a strobe on the ignition wire should show it too.
Sox
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Old 04-02-2018, 03:45 PM
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