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Jumpy Tach?

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Old 04-16-2012, 12:54 PM
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Car: 1984 Trans Am
Engine: LS1383 in work
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Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Jumpy Tach?

Hey guys,

84 T/A, 355, CC Qjet. Factory Distributor (138K miles), melonized gear for the roller cam.

The tach started jumping around today, anywhere from 500rpm to 1000rpm. At the stop light, when it jumped, it felt like the engine surged a bit. When gunning it and the RPM's going up, it'll jump and the car will feel like it's stuttering. Shorted plug wire? Bad dizzy? Any ideas?
Old 04-16-2012, 11:41 PM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
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Axle/Gears: 3.54 Dana 44
Re: Jumpy Tach?

Misfire
Old 04-17-2012, 06:53 AM
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Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Jumpy Tach?

Originally Posted by Apeiron
Misfire
That's kind of what I was thinking, just wanted to bounce some ideas around.
Old 04-17-2012, 03:21 PM
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Car: 1984 Trans Am
Engine: LS1383 in work
Transmission: Magnum F
Axle/Gears: Zexel Torsen 3.73, 28-spline mosers
Re: Jumpy Tach?

Originally Posted by Apeiron
Misfire
I pulled my cap off and found one of the rotor screws missing. It was down under the rotor and there were scratch marks all over the inside. Tightened it down and ranRit for fivea oe minutes, tach didn't jump. My guess is that it was shorting to the screw that was being tossed around the inside there. I also swapped in a different cap that I had from a spare dizzy that I had lying around. Hopefully it was that screw.
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