Ignition Timing Not Advancing

[BMD273]

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

[kdjones2000]

Look at the "DME Test Plan" for direction on this.

I would also get a new mechanic...

[DannoXYZ]

Originally Posted by BMD273

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.

[soxnail]

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