LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

What tells the PCM which RPM it's at?

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Old 04-19-2004, 01:30 PM
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What tells the PCM which RPM it's at?

What sensor tells PCM which RPMs is the car running? Optispark? What exactly? 3X low res signal? I have problem (from a looong time) with RPM running all over the place at idle (like 1000 - 1100 - 4375 (!) - 900 etc). Something tells very high RPMs (well, the engine shakes, so turns faster, but not like 4k RPM in a split of a second!) and I want to find it.
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Old 04-19-2004, 02:10 PM
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I believe it's the pulse of the coil.
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Old 04-19-2004, 02:32 PM
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The low res pulse from the Opti.
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