C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
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Old Dec 1, 2010 | 03:10 PM
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From: Lubbock TX
Default jumpy tach

79 L82, When the engine starts up cold, tach jumps up 3-400rpm until engine warms up good. When I say jumps, lets say if it is idling at 1200 or so, it might jump up to 15-1600 but never below the 1200. What is causing this and can it be fixed?
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Old Dec 1, 2010 | 04:01 PM
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The tach circuit board is usually the culprit. They just go bad after many years of use. Easy fix. Replace the board, most vendors carry this piece.
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