Tach always twitching
03-17-09, 10:01 PM
#1
Tach always twitching
My tach is always jumping wildly all over the place. 30% of the time when your just cruising with the same throttle input it gives a steady reading and at idle. When your revving or accelerating it will bounce all over the place. I know that by the sound of the engine I'm around 3500 RPM but the needle shoots up to 8000 and the buzzer sounds off.
This problem has been going on for a few weeks now, and although it doesn't affect the performance of the car, it is VERY annoying! Where should I begin to look? I figured first thing to do is find a cheap replacement dizzy. Are there any other grounds or anything in particular that go bad on this car?
The problem seems to have started when I installed my Autometer water temp gauge. Maybe I'll try taking it out to see if the ground I tapped into is a problem.
This problem has been going on for a few weeks now, and although it doesn't affect the performance of the car, it is VERY annoying! Where should I begin to look? I figured first thing to do is find a cheap replacement dizzy. Are there any other grounds or anything in particular that go bad on this car?
The problem seems to have started when I installed my Autometer water temp gauge. Maybe I'll try taking it out to see if the ground I tapped into is a problem.
03-18-09, 11:47 AM
#3
Grey-Bruce Rotorhead
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It could be a grounding issue. However, I would try switching your two ignitors with each other. If you have a third one laying around, then just replace your trailing ignitor with it. The tach reads off of the trailing ignitor. When they go bad, they cause the tach to go nuts. It's happened with me a couple of times where my car would start to spit and stutter out of the blue. I swapped the two ignitors and sure enough, the car runs perfectly, but the tach goes crazy.
03-18-09, 03:53 PM
#4
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if you have the points distributor still, it needs points.
if you have the electronic one, maybe you have a flakey connection, or an ignitor failing, or a bad cap and rotor
if you have the electronic one, maybe you have a flakey connection, or an ignitor failing, or a bad cap and rotor
03-18-09, 10:06 PM
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you could also adjust/replace the points, but they do need regular attention
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03-19-09, 03:32 AM
#8
berlinetta
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http://www.mazspeed.com/ignitionswap.htm
great walkthrough on points to electronic dizzy swap.
or get a MSD and direct fire...
great walkthrough on points to electronic dizzy swap.
or get a MSD and direct fire...
03-19-09, 03:35 AM
#9
berlinetta
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It could be a grounding issue. However, I would try switching your two ignitors with each other. If you have a third one laying around, then just replace your trailing ignitor with it. The tach reads off of the trailing ignitor. When they go bad, they cause the tach to go nuts. It's happened with me a couple of times where my car would start to spit and stutter out of the blue. I swapped the two ignitors and sure enough, the car runs perfectly, but the tach goes crazy.
the tach signal comes from the leading on 79 models.
03-19-09, 06:59 PM
#10
Grey-Bruce Rotorhead
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