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Old 10-28-2017, 08:47 PM   #209
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Broke4speed's Avatar
Join Date: Oct 2009
Location: Marionville, Ontario, Canada

Well, setbacks all around.
The trigger wheel works, but at 4500-ish rpm, it begins to break up and backfire. I'm getting sync loss reason #2, which means missing tooth at wrong time. The sensor is as close as I can get it to the wheel, the shielded trigger wire isn't near any of the coilpack wiring (until it gets to the harness anyway, but they're logic outputs so I'd imagine the noise is minimal), the plug wires are new (GM six-banger 3.8L wires, minus two), and higher RPM brrrrrrrrraaaaaaaaaaaaaapppppppppppBANGBANGBANG. I'm free-revving too, no load, so I'm lost.

This MS2 is a DIYautotune-built box, v3.57 PCB, and the only mod I've done to it is add the second spark output for the wasted spark coilpack. I had a similar problem with the MS1 box I was using previously, but assumed it was a weak coil. I'm stumped now, because how could two different computers, two different wiring harnesses, and two different ignition types (single coil with dizzy and wasted spark with trigger wheel), both have the same issue?

Maybe I've got a bad valve spring, or they're just too old and worn, and I'm getting float? I can't see how, at such a low RPM, but at this point I have no idea. I'm very tempted to pull everything, part out the B21 stuff, and find a swap.
1984 244/ AQ140A / M46
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